Landfill gas extraction systems and methods

ABSTRACT

Described herein are embodiments of a control system that automatically (1) determines whether a gas extraction system is in a state in which landfill gas is being released into the atmosphere, and (2) automatically controls landfill gas flow to mitigate, prevent and/or stop the release of landfill gas. The control system may control a valve to control flow of landfill gas through well piping of the gas extraction system. The pressure of landfill gas in the well piping at a location upstream of the valve may indicate whether there is a risk of landfill gas being released into the atmosphere. The control system may adjust a position of the valve in response to determining that the pressure at the location upstream of the valve indicates that there is a risk of landfill gas being released into the atmosphere.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application claims the benefit of priority under 35 U.S.C. §119 (e) to U.S. provisional patent application No. 62/739,612, titled“FIELD LEVEL CONTROL OF LANDFILL GAS EXTRACTION”, filed on Oct. 1, 2018,attorney docket number L0789.70009US00, and U.S. provisional patentapplication No. 62/793,304, titled “PRESSURE CONTROL IN LANDFILL GASEXTRACTION SYSTEMS”, filed on Jan. 16, 2019, attorney docket numberL0789.70009US01, each of which is incorporated by reference herein inits entirety.

FEDERALLY SPONSORED RESEARCH

This invention was made with government support under SBIR Phase IIAward No. 1632439 and SBIR Phase 1B Award No. 1520346, awarded by theNational Science Foundation. The government has certain rights in theinvention.

BACKGROUND

Landfills typically produce landfill gas as a result of decompositionprocesses occurring in the waste, and methane is often a component ofthis landfill gas. In order to reduce emissions of methane and othercontaminants in landfill gas, the landfill sites are typically cappedwith a layer of cover material and gas extraction systems are installedto pull landfill gas out before it can penetrate the cover layer andescape. At larger sites, these gas extraction systems can consist of aplurality of vertical and horizontal wells drilled into the landfill,which are connected with piping to one or more vacuum sources. The coverlayer prevents gas from freely escaping, while the vacuum in theextraction wells pulls landfill gas into the collection system. Aconventional landfill gas extraction well typically has a manual valvethat adjusts the localized vacuum pressure in that well, as well as aset of ports for sampling the gas characteristics with a portable gasanalyzer. Landfill gas is most often disposed of in a flare, processedfor direct use, or used to power electricity generation equipment (suchas generators or gas turbines).

SUMMARY

Some embodiments are directed to a control system for controllingextraction of landfill gas from a landfill via a gas extraction system,the gas extraction system comprising well piping for coupling aplurality of wells to a gas output, the control system comprising acontroller configured to: obtain a value indicating measured energycontent of landfill gas collected at the gas output from the pluralityof wells; determine whether the measured energy content is differentfrom a target energy content; and in response to determining that themeasured energy content is different from the target energy contentcontrol a plurality of valves disposed in the well piping to change flowrates of landfill gas being extracted from at least some of theplurality of wells at least in part by changing degrees to which theplurality of valves are open.

In some embodiments, controlling the plurality of valves disposed in thewell piping comprises: determining a value of a control adjustment; andtransmitting the value of the control adjustment to a plurality ofcontrollers, each of at least some of the plurality of controllersconfigured to control a respective one of the plurality of valves.

In some embodiments, the gas output comprises a power plant and thecontroller is further configured to obtain the value indicating themeasured energy content of landfill gas from the power plant.

In some embodiments, the controller comprises a PID controllerconfigured to receive, as input, a difference between the measuredenergy content and the target energy content.

In some embodiments, the controller is further configured to: determinethat the target energy content is greater than the measured energycontent; and in response to determining that the target energy contentis greater than the measured energy content, controlling the pluralityof valves to decrease the flow rates of landfill gas through the atleast some of the plurality of wells.

In some embodiments, the controller is further configured toconcurrently control the plurality of valves.

In some embodiments, the gas output comprises a processing plantconfigured to treat landfill gas collected at the gas output.

Some embodiments are directed to a control system for controllingextraction of landfill gas from a landfill via a gas extraction system,the gas extraction system comprising well piping for coupling aplurality of wells to a gas output, the control system comprising: acontroller configured to: obtain a value indicating measured energycontent of landfill gas collected at the gas output from the pluralityof wells; determine whether the measured energy content is within atarget range of energy content; and in response to determining that themeasured energy content is not within the target range of energycontent: control a plurality of valves disposed in the well piping tochange flow rates of landfill gas being extracted from at least some ofthe plurality of wells at least in part by changing degrees to which theplurality of valves are open.

In some embodiments, controlling the plurality of wells comprises:determining a control adjustment; and transmitting the controladjustment to a plurality of controllers, each of at least some of theplurality of controllers configured to control a respective one of theplurality of valves.

In some embodiments, the controller is further configured to: set thecontrol adjustment to a first value in response to determining that themeasured energy content is less than a first threshold content; and setthe control adjustment to a second value different from the first valuein response to determining that the measured energy content is greaterthan a second threshold content.

In some embodiments, controlling the flow rates of landfill gas frombeing extracted from the at least some wells comprises: identifying asubset of the at least some wells; and adjusting flow rates of landfillgas being extracted from the subset of wells.

In some embodiments, the controller is further configured to identifythe subset of the at least some wells based on a concentrations ofmethane in landfill gas being extracted from the at least some wells.

Some embodiments are directed to a system for controlling extraction oflandfill gas from a landfill via a gas extraction system, the gasextraction system comprising a vacuum source, well piping, and a wellcoupled to the vacuum source through the well piping, the systemcomprising: at least one flow control mechanism disposed in the wellpiping and configured to control flow rate of landfill gas through thegas extraction system; and a controller configured to: determine one ormore control variables using one or more measurements selected from thegroup consisting of a change in pressure of the vacuum source, a changein barometric pressure outside of the landfill, a change in ambienttemperature outside of the landfill and a quality of aggregated landfillgas received at a gas output; control the at least one flow controlmechanism based at least on the one or more control variables.

In some embodiments, the at least one control mechanism comprises avalve, and controlling the at least one flow control mechanism comprisesproviding a command to an actuator to cause the actuator to adjust aposition of the valve.

In some embodiments, the one or more control variables comprise aplurality of control variables and controlling the at least one flowcontrol mechanism comprises: combining the plurality of controlvariables to obtain an adjustment to the at least one flow controlmechanism; and applying the adjustment to the at least one flow controlmechanism.

In some embodiments, the controller is configured to obtain theadjustment to the at least one flow control mechanism at least in partby: applying a respective gain parameter to each of at least some of theplurality of control variables to obtain a plurality of adjustments; andcombining the plurality of adjustments to obtain the adjustment to theat least one flow control mechanism.

In some embodiments, the controller is further configured to control theat least one flow control mechanism to decrease the flow rate oflandfill gas through the gas extraction system in response todetermining an increase in barometric pressure over a period of time.

In some embodiments, the controller is configured to control the atleast one flow control mechanism to decrease the flow rate of landfillgas through the gas extraction system in response to determining adecrease in temperature over a period of time.

In some embodiments, the controller is configured to control the atleast one flow control mechanism to decrease the flow rate of landfillgas through the gas extraction system in response to determining anincrease in vacuum pressure.

In some embodiments, the controller is configured to control the atleast one flow control mechanism to change the flow rate of landfill gasthrough the gas extraction system in response to determining a change inbarometric pressure, a change in temperature, and/or a change in vacuumpressure.

Some embodiments provide for a control system for controlling extractionof landfill gas from a landfill via a gas extraction system, the gasextraction system comprising well piping for coupling a well to a gasoutput, the control system comprising: a valve for controlling flow oflandfill gas through the well piping to the gas output; a pressuresensor configured to measure landfill gas pressure in the well piping ata location upstream of the valve; and a controller configured to:obtain, using the pressure sensor, a first measurement of the landfillgas pressure at the location upstream of the valve; determine whetherthe first measurement of the landfill gas pressure at the locationupstream of the valve is greater than a first threshold pressure; and inresponse to determining that the first measurement of the landfill gaspressure at the location upstream of the valve is greater than the firstthreshold pressure, control the valve to reduce the landfill gaspressure at the location upstream of the valve.

In some embodiments, the controller is configured to control the valveto reduce the landfill gas pressure in the well piping at the locationupstream of the valve by increasing a degree to which the valve is open.

In some embodiments, the controller is configured to control the valveto reduce the landfill gas pressure in the well piping at the locationupstream of the valve by: obtaining a second measurement of landfill gaspressure in the well piping at a location downstream of the valve;determining whether the second measurement of the landfill gas pressureat the location downstream of the valve is less than a second thresholdpressure; and increasing the degree to which the valve is open only inresponse to determining that the second measurement of the landfill gaspressure at the location downstream of the valve is less than the secondthreshold pressure.

In some embodiments, the controller is configured to control the valveto reduce the landfill gas pressure at the location upstream of thevalve by maintaining a position of the valve in response to determiningthat the second measurement of the landfill gas pressure at the locationdownstream of the valve is greater than the second threshold pressure.

In some embodiments, the second threshold pressure is approximately 0mbar. In some embodiments, the first threshold pressure is approximately−0.1 mbar.

In some embodiments, the controller is configured to control the valveto reduce the landfill gas pressure in the well piping at the locationupstream of the valve by: increasing a degree to which the valve is openby a first amount; and after increasing the degree to which the valve isopen by the first amount: obtaining, from the pressure sensor, a secondmeasurement of the landfill gas pressure at the location upstream of thevalve; and in response to determining that the second measurement of thelandfill gas pressure at the location upstream of the valve is greaterthan the first threshold pressure, increasing the degree to which thevalve is open by the first amount.

In some embodiments, the controller is configured to: in response todetermining that the first measurement of the landfill gas pressure atthe location upstream of the valve is greater than the first thresholdpressure: store a record of the first measurement of the landfill gaspressure at the location upstream of the valve; store a record ofcontrolling the valve to reduce the landfill gas pressure at thelocation upstream of the valve; and store a record of a secondmeasurement of the landfill gas pressure at the location upstream of thevalve after controlling the valve to reduce the landfill gas pressure atthe location upstream of the valve.

In some embodiments, the controller is configured to store the record ofthe second measurement of the landfill gas pressure at the locationupstream of the valve when it is determined that the second measurementis less than the first threshold pressure.

In some embodiments, the control system of claim 1, wherein thecontroller is configured to control the valve to reduce the landfill gaspressure at the location upstream of the valve by: implementing one ormore adjustments in position of the valve determined by the controllerfor reducing the landfill gas pressure at the location upstream of thevalve; and not implementing one or more other adjustments in theposition of the valve determined by the controller.

In some embodiments, the controller is configured to: in response todetermining that the first measurement of the landfill gas pressure atthe location upstream of the valve is less than or equal to the firstthreshold pressure, control the valve by maintaining a position of thevalve.

Some embodiments provide for a method of controlling extraction oflandfill gas from a landfill via a gas extraction system, the methodcomprising: obtaining, from a pressure sensor, a first measurement oflandfill gas pressure at a location upstream of a valve in well pipingof the gas extraction system, the valve being for controlling flow oflandfill gas through the well piping from the landfill to a gas output;determining whether the first measurement of the landfill gas pressureat the location upstream of the valve is greater than a first thresholdpressure; and in response to determining that the first measurement ofthe landfill gas pressure at the location upstream of the valve isgreater than the first threshold pressure, controlling the valve toreduce the landfill gas pressure at the location upstream of the valve.

In some embodiments, the method further comprises controlling the valveto reduce the landfill gas pressure in the well piping at the locationupstream of the valve by increasing a degree to which the valve is open.

In some embodiments, the method further comprises controlling the valveto reduce the landfill gas pressure in the well piping at the locationupstream of the valve by: obtaining a second measurement of landfill gaspressure in the well piping at a location downstream of the valve;determining whether the second measurement of the landfill gas pressureat the location downstream of the valve is less than a second thresholdpressure; and increasing the degree to which the valve is open only inresponse to determining that the second measurement of the landfill gaspressure at the location downstream of the valve is less than the secondthreshold pressure.

In some embodiments, the method further comprises controlling the valveto reduce the landfill gas pressure at the location upstream of thevalve by maintaining a position of the valve in response to determiningthat the second measurement of the landfill gas pressure at the locationdownstream of the valve is greater than the second threshold pressure.

In some embodiments, the second threshold pressure is approximately 0mbar. In some embodiments, the first threshold pressure is approximately−0.1 mbar.

In some embodiments, the method further comprises controlling the valveto reduce the landfill gas pressure in the well piping at the locationupstream of the valve by: increasing a degree to which the valve is openby a first amount; and after increasing the degree to which the valve isopen by the first amount: obtaining, from the pressure sensor, a secondmeasurement of the landfill gas pressure at the location upstream of thevalve; and in response to determining that the second measurement of thelandfill gas pressure at the location upstream of the valve is greaterthan the first threshold pressure, increasing the degree to which thevalve is open by the first amount.

In some embodiments, the method further comprises: in response todetermining that the first measurement of the landfill gas pressure atthe location upstream of the valve is greater than the first thresholdpressure: storing a record of the first measurement of landfill gaspressure at the location upstream of the valve; storing a record ofcontrolling the valve to reduce the landfill gas pressure at thelocation upstream of the valve; and storing a record of a secondmeasurement of the landfill gas pressure at the location upstream of thevalve after controlling the valve to reduce the landfill gas pressure atthe location upstream of the valve.

In some embodiments, the method further comprises storing the record ofthe second measurement of the landfill gas pressure at the locationupstream of the valve when it is determined that the second measurementis less than the first threshold pressure.

In some embodiments the method further comprises controlling the valveto reduce the landfill gas pressure at the location upstream of thevalve by: implementing one or more adjustments in position of the valvedetermined by the controller for reducing the landfill gas pressure atthe location upstream of the valve; and not implementing one or moreother adjustments in the position of the valve determined by thecontroller.

In some embodiments, the method further comprises in response todetermining that the first measurement of the landfill gas pressure atthe location upstream of the valve is less than or equal to the firstthreshold pressure, controlling the valve by maintaining a position ofthe valve.

Some embodiments provide for a control system for controlling extractionof landfill gas from a landfill via a gas extraction system, the gasextraction system comprising well piping for coupling a well to a gasoutput, the control system comprising: a controller configured to:obtain a first measurement of landfill gas pressure at a locationupstream of a valve disposed in the well piping, the valve being forcontrolling flow of landfill gas through the well piping to the gasoutput; determine whether the first measurement of the landfill gaspressure at the location upstream of the valve is greater than a firstthreshold pressure; and in response to determining that the firstmeasurement of the landfill gas pressure at the location upstream of thevalve is greater than the first threshold pressure, control the valve toreduce the landfill gas pressure at the location upstream of the valve.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects and embodiments will be described with reference to thefollowing figures. It should be appreciated that the figures are notnecessarily drawn to scale. For purposes of clarity, not every componentmay be labeled in every drawing. In the drawings:

FIG. 1 is a sketch illustrating a landfill gas extraction system,according to some embodiments;

FIG. 2 is a block diagram illustrating an in situ control mechanism forlandfill gas extraction, according to some embodiments;

FIG. 3 is a block diagram illustrating a gas analyzer of an in situcontrol mechanism for landfill gas extraction, according to someembodiments;

FIG. 4 is a block diagram illustrating a controller of an in situcontrol mechanism for landfill gas extraction, according to someembodiments;

FIG. 5 is a block diagram illustrating an example of a control systemfor controlling landfill gas extraction, according to some embodiments;

FIG. 6 is a block diagram illustrating an example of a feedback-based,predictive system for controlling landfill gas extraction, according tosome embodiments;

FIG. 7 is a flow diagram illustrating another example of afeedback-based, predictive system for controlling landfill gasextraction, according to some embodiments;

FIG. 8 is a sketch of an example of zones of influence of wells in alandfill;

FIG. 9 is a sketch of another example of zones of influence of wells ina landfill;

FIG. 10 is a flowchart of an illustrative process for controllingextraction of landfill gas from a landfill through a gas extractionsystem, according to some embodiments;

FIG. 11 is a block diagram of an exemplary computer system in whichaspects of the present disclosure may be implemented, according to someembodiments;

FIG. 12 is a flowchart of another illustrative process for controllingextraction of landfill gas through a gas extract system, according tosome embodiments;

FIG. 13 is a flowchart of another illustrative process for controllingextraction of landfill gas through a gas extract system, according tosome embodiments;

FIG. 14 is a flowchart of another illustrative process for controllingextraction of landfill gas through a gas extract system, according tosome embodiments;

FIG. 15 is an example of a landfill gas extraction system, according tosome embodiments;

FIG. 16 is a flowchart of an illustrative process for controllingextraction of landfill gas from multiple gas extraction wells, accordingto some embodiments;

FIG. 17 is a block diagram of an illustrative control system for locallycontrolling flow of landfill gas at a gas extraction well, according tosome embodiments;

FIG. 18 is a block diagram of an illustrative control system forglobally controlling flow of landfill gas at multiple gas extractionwells, according to some embodiments;

FIG. 19 is a flowchart of an illustrative process for performing globalerror recovery at multiple gas extraction wells, according to someembodiments;

FIG. 20 is an example of a landfill gas extraction system, according tosome embodiments; and

FIG. 21 is a flow chart of a process for controlling pressure in alandfill gas extraction system, according to some embodiments.

DETAILED DESCRIPTION

Conventional techniques for controlling extraction of landfill gas aresometimes imprecise and inefficient. When such techniques are used, thegas extracted from a landfill may not have the desired properties (e.g.,the energy content of the extracted gas may be lower than a desiredenergy content, the composition of the extracted gas may differ from adesired composition, etc.). In some cases, conventional techniques mayeven be counter-productive (e.g., such techniques may destroy some orall of the bacteria that convert decomposing waste into methane, therebyreducing the energy content of the landfill gas, or may result inemission of high levels of methane into the atmosphere, or worse yet,cause fires to break out deep within the landfill that are nearimpossible to extinguish).

The inventors have recognized and appreciated that controllingextraction of landfill gas based on a predictive model of the landfillmay overcome at least some of the deficiencies of conventional landfillgas extraction techniques and result in an overall improvement inlandfill management. For example, controlling extraction of landfill gasbased on a predictive model of the landfill may increase precisionand/or efficiency of the gas extraction process, thereby facilitatingextraction of landfill gas having desired properties. As anotherexample, controlling extraction of landfill gas based on a predictivemodel of the landfill may reduce the landfill's environmental impact(e.g., by reducing the amount of harmful and/or foul-smelling gasemitted into the atmosphere). In some embodiments, the performance ofthe gas extraction system may be enhanced by adjusting the system'scontrol settings in real time or at frequent intervals (e.g., hourly ordaily). In some embodiments, the performance of the gas extractionsystem may be enhanced by training the predictive model based ondifferences between the landfill state predicted by the model and thelandfill state actually observed. In some embodiments, the performanceof the gas extraction system may be enhanced by modeling interactionsbetween/among two or more wells. The inventors have recognized thatadjustments in one well may lead to changes in the conditions ofsurrounding wells. Modeling interactions among two or more wells and theuse of predictive modeling as described herein allows for automatedcontrol among multiple wells.

As described above, conventional techniques for controlling extractionof landfill gas may result in extraction of landfill gas having acomposition that is different from a target composition. Accordingly,the inventors have developed techniques for controlling extraction oflandfill gas such that the concentration of each of one or moreconstituent gases is in a respective target range. For example, some ofthe techniques described herein may be used to control extraction oflandfill gas so that the concentration of methane in the landfill gasbeing extracted is within a target range (e.g., within 45-55% byvolume).

In some embodiments, an iterative control technique may be used tocontrol extraction of landfill gas such that the concentration of aparticular gas (e.g., methane, oxygen, nitrogen, etc.) falls within atarget range such that the concentration is above a first thresholdconcentration and below a second threshold concentration. The first andsecond threshold concentrations may define the target range, with thesecond threshold concentration being greater than (or equal to, in someembodiments) the first threshold concentration.

Accordingly, in some embodiments, a control system for controllingextraction of landfill gas may include: (A) at least one sensorconfigured to measure one or more characteristics of landfill gasextracted from the landfill; (B) at least one flow control mechanismdisposed in well piping and configured to control flow of the landfillgas through the well piping; and (C) at least one processor configuredto: (1) obtain a measured concentration, obtained using the at least onesensor, of a first gas in landfill gas extracted from the landfill; (2)determine whether the measured concentration of the first gas is eitherless than a first threshold concentration or greater than a secondthreshold concentration (e.g., whether a measured concentration ofmethane is less than 45% by volume or greater than 55% by volume); (3)when it is determined that the measured concentration is less than thefirst threshold concentration, control the at least one flow controlmechanism to reduce (e.g., when the first gas is methane) or increase(e.g., when the first gas is oxygen or nitrogen) the flow rate oflandfill gas through the at least one flow control mechanism; and (4)when it is determined that the concentration is greater than the secondthreshold concentration, control the at least one flow control mechanismto increase (e.g., when the first gas is methane) or to decrease (e.g.,when the first gas is oxygen or nitrogen) the flow rate of landfill gasthrough the at least one flow control mechanism.

In some embodiments, when it is determined that the measuredconcentration is less than the first threshold concentration, the atleast one processor is further configured to: after controlling the atleast one flow control mechanism to reduce the flow rate of the landfillgas through the at least one flow control mechanism, (1) obtain a secondmeasured concentration of the first gas in landfill gas extracted fromthe landfill; (2) determine whether the second measured concentration ofthe first gas is less than the first threshold concentration; and (3)when it is determined that the second measured concentration of thefirst gas is less than the first threshold concentration, control the atleast one flow control mechanism to further reduce the flow rate oflandfill gas through the at least one flow control mechanism.

Similarly, in some embodiments, when it is determined that the measuredconcentration is greater than the second threshold concentration, the atleast one processor is further configured to: after controlling the atleast one flow control mechanism to increase the flow rate of thelandfill gas through the at least one flow control mechanism, (1) obtaina second measured concentration of the first gas in landfill gasextracted from the landfill; (2) determine whether the second measuredconcentration of the first gas is greater than the second thresholdconcentration; and (3) when it is determined that the second measuredconcentration of the first gas is greater than the second thresholdconcentration, control the at least one flow control mechanism tofurther increase the flow rate of landfill gas through the at least oneflow control mechanism.

In some embodiments, the at least one flow control mechanism may includeone or more valves. Examples of different types of valves are providedherein. In some embodiments, the at least one processor may beconfigured to control the at least one flow control mechanism toincrease the flow rate of landfill gas at least in part by causing oneor more valve(s) to open to a greater degree (e.g., to open by aspecified increment or in any other suitable way). The at least oneprocessor may be configured to control the at least one flow controlmechanism to decrease the flow rate of landfill gas at least in part bycausing one or more valves to close to a greater degree.

In some embodiments, the sensor(s) configured to measure landfill gascharacteristics may include sensor(s) configured to measure partialpressure and/or concentrations of gases including, but not limited to,methane, oxygen, carbon dioxide, carbon monoxide, hydrogen sulfide, andnitrogen. Examples of such sensors are provided herein. In someembodiments, the sensor(s) may be co-located with the at least one flowcontrol mechanism. For example, the sensor(s) and the flow controlmechanism (e.g., a valve) may be part of an in situ control mechanism(e.g., in situ control mechanism 200 described with reference to FIG.2).

In some embodiments, the at least one processor may be located remotelyfrom the at least one flow control mechanism and may be configured tocommunicate with the at least one flow control mechanism using one ormore wireless links, one or more wired links, or any suitablecombination thereof.

Also as described above, conventional techniques for controllingextraction of landfill gas may result in extraction of landfill gashaving energy content lower than a targeted energy content. Accordingly,the inventors have developed techniques for controlling extraction oflandfill gas such that the energy content in the extracted gas ismaximized or at least higher than the energy content would otherwise bewith the application of conventional methods. The inventors appreciatedthat the product of the flow rate of extracted landfill gas and theconcentration of methane in the extracted landfill gas, which mayindicate the rate of methane extraction, provides a good estimate of theenergy content in the extracted landfill gas, as methane is a majorsource of energy extracted from landfills (e.g., energy may be generatedby burning methane). Accordingly, some of the techniques developed bythe inventors seek to achieve as high a product of methane concentrationand flow rate as possible. In some embodiments, the techniques involveiteratively adjusting the flow rate of extracted landfill gas, based onflow rate and methane concentration measurements, so as to maximize theproduct of methane concentration and extracted landfill gas flow rate.

Accordingly, in some embodiments, a control system for controllingextraction of landfill gas may include: (A) at least one sensorconfigured to measure one or more characteristics of landfill gasextracted from the landfill; (B) at least one flow control mechanismdisposed in well piping and configured to control flow of the landfillgas through the well piping; and (C) at least one processor configuredto perform: (1) obtaining, based on at least one first measurementobtained using the at least one sensor, a first measure of energycontent in a first portion of extracted landfill gas; (2) controllingthe at least one flow control mechanism to increase a flow rate oflandfill gas being extracted from the landfill; (3) after thecontrolling, (a) obtaining, based on at least one second measurementobtained using the at least one sensor, a second measure of energycontent in a second portion of extracted landfill gas; determiningwhether the second measure of energy content is greater than the firstmeasure of energy content; (b) when it is determined that the secondmeasure of energy content is greater than the first measure of energycontent, controlling the at least one flow control mechanism to increasethe flow rate of landfill gas being extracted from the landfill; and (c)when it is determined that the second measure of energy content is lessthan the first measure of energy content, controlling the at least oneflow control mechanism to decrease the flow rate of landfill gas beingextracted from the landfill.

In some embodiments, obtaining the first measure of energy contentcomprises: obtaining a measurement of a first concentration of methanein the first portion of extracted landfill gas and a measurement of afirst flow rate of landfill gas through the at least one flow controlmechanism; and determining the first measure of energy content based onthe first concentration of methane and the first flow rate of landfillgas. In some embodiments, obtaining the second measure of energy contentcomprises: obtaining a measurement of a second concentration of methanein the second portion of extracted landfill gas and a second flow rateof landfill gas through the at least one flow control mechanism; anddetermining the second measure of energy content based on the secondconcentration of methane and the second flow rate of landfill gas.

In some embodiments, the techniques for controlling the extraction oflandfill gas may seek to maximize energy content in the landfill gassubject to one or more constraints on the concentration(s) of one ormore other gases. For example, in some embodiments, the techniques forcontrolling landfill gas extraction may seek to maximize energy contentin the landfill gas (or satisfy any other objective described herein)subject to an upper limit (e.g., 2.5%) on the concentration of nitrogenin the extracted gas. The concentration of nitrogen may be measureddirectly (e.g., using one or more sensors) or indirectly (e.g., bymeasuring concentrations of methane, oxygen, and carbon dioxide andestimating the concentration of nitrogen as the remaining balance gas,for example, by estimating the concentration of nitrogen as100%-concentration of methane—concentration of oxygen—concentration ofmethane). Limits on concentration of nitrogen may be imposed by landfilloperators, operators of associated power generation facilities, localregulations, state regulations, and/or federal regulations.

Accordingly, in some embodiments, the at least one processor of thecontrol system may be further configured to perform: (1) obtaining, fromthe at least one sensor, measured concentrations of methane, oxygen, andcarbon dioxide in the first portion of extracted landfill gas; (2)determining a balance gas concentration based on the measuredconcentrations of methane, oxygen, and carbon dioxide; (3) controllingthe at least one flow control mechanism to increase the flow rate oflandfill gas being extracted from the landfill only when it isdetermined both that the second measure of energy content is greaterthan the first measure of energy content and the balance gasconcentration is less than a balance gas threshold (e.g., 2.5% byvolume); and (4) controlling the at least one flow control mechanism todecrease the flow rate of landfill gas being extracted from the landfillwhen it is determined that either the second measure of energy contentis less than the first measure of energy content or the balance gasconcentration is greater than the balance gas threshold.

As another example, in some embodiments, the techniques for controllinglandfill gas extraction may seek to maximize energy content in thelandfill gas (or satisfy any other objective described herein) subjectto an upper limit (e.g., 5%) on the concentration of oxygen in theextracted gas. Limiting the amount of oxygen in the extracted landfillgas may be helpful because high amounts of oxygen may negativelyinfluence how generators run, for example, by causing engine problems orcontributing to fires deep within the landfill. Limits on theconcentration of oxygen may be imposed by landfill operators, powerutility operators, local regulations, state regulations, and/or federalregulations.

Accordingly, in some embodiments, the at least one processor of thecontrol system may be further configured to perform: (1) obtaining, fromthe at least one sensor, a measured concentration of oxygen in the firstportion of extracted landfill gas; (2) controlling the at least one flowcontrol mechanism to increase the flow rate of landfill gas beingextracted from the landfill only when it is determined both that thesecond measure of energy content is greater than the first measure ofenergy content and the measured concentration of oxygen is less than anoxygen threshold (e.g., 5% by volume); and (3) controlling the at leastone flow control mechanism to decrease the flow rate of landfill gasbeing extracted from the landfill when it is determined that either thesecond measure of energy content is less than the first measure ofenergy content or the measured concentration of oxygen is greater thanthe oxygen threshold.

The inventors have also appreciated that changes in atmospheric pressure(e.g., due to weather changes) may cause changes in the composition oflandfill gas. For example, the percentage of methane in landfill gas mayincrease during periods of declining atmospheric pressure and maydecrease during periods of increasing atmospheric pressure. Accordingly,the inventors have developed techniques for controlling extraction oflandfill gas based on atmospheric pressure measurements and changesamong them. In some embodiments, the flow rate of landfill gas beingextracted may be decreased in response to increasing atmosphericpressure and/or increased in response to decreasing atmosphericpressure.

Accordingly, in some embodiments, a control system for controllingextraction of landfill gas may include: (A) at least one atmosphericpressure sensor configured to measure atmospheric pressure; (B) at leastone flow control mechanism disposed in well piping and configured tocontrol flow of the landfill gas through the well piping; and (C) atleast one processor configured to perform: (1) obtaining a firstatmospheric pressure value based on at least one first measurementobtained by the at least one atmospheric pressure sensor; (2) obtaininga second atmospheric pressure value based on at least one secondmeasurement obtained by the at least one atmospheric pressure sensorafter obtaining the at least one first measurement; (3) determiningwhether the second atmospheric pressure value is greater than the firstatmospheric pressure value; (4) when it is determined that the secondatmospheric pressure value is greater than the first atmosphericpressure value, controlling the at least one flow control mechanism todecrease the flow rate of landfill gas being extracted from thelandfill; and (5) when it is determined that the second atmosphericpressure value is less than the first atmospheric pressure value,controlling the at least one flow control mechanism to increase the flowrate of landfill gas being extracted from the landfill.

In some embodiments, after controlling the at least one flow controlmechanism to decrease the flow rate of landfill gas being extracted fromthe landfill, the control system may further perform: (1) obtaining athird atmospheric pressure value based on at least one third measurementobtained by the at least one atmospheric pressure sensor after obtainingthe at least one second measurement; (2) determining whether the thirdatmospheric pressure value is greater than the second atmosphericpressure value; (3) when it is determined that the third atmosphericpressure value is greater than the second atmospheric pressure value,controlling the at least one flow control mechanism to further decreasethe flow rate of landfill gas being extracted from the landfill; and (4)when it is determined that the third atmospheric pressure value is lessthan the second atmospheric pressure value, controlling the at least oneflow control mechanism to increase the flow rate of landfill gas beingextracted from the landfill.

In some embodiments, the control system may be configured to change theflow rate of landfill gas being extracted by an amount determined basedon the magnitude of change in the atmospheric pressure. For example, inresponse to a small relative change in atmospheric pressure, the controlsystem may effect a small change in a valve of other flow controlmechanism. By contrast, a valve or other flow control mechanism may beadjusted by a larger amount in response to a greater change inatmospheric pressure.

The aspects and embodiments described above, as well as additionalaspects and embodiments, are described further below. These aspectsand/or embodiments may be used individually, all together, or in anycombination, as the application is not limited in this respect.

This disclosure describes devices and techniques for controllinglandfill gas extraction. FIG. 1 illustrates a landfill gas extractionsystem 100, according to some embodiments. In some embodiments, alandfill gas extraction system may include one or more gas extractionwells 102 coupled to one or more wellheads 104. In some embodiments,each wellhead may be in fluid communication with a single, correspondingwell. In some embodiments, the landfill gas extraction system 100 mayinclude a gas extraction piping system 108 coupling the well(s) 102 to agas collection system 110, and one or more In Situ Control Mechanisms106 for controlling extraction of the landfill gas through the well(s)102 and gas extraction piping system 108 to the gas collection system110. In some embodiments, gas collection system 110 may supply theextracted landfill gas to a gas-to-energy power plant 112, which mayconvert the landfill gas into electrical power (e.g., by burning thelandfill gas to turn the rotor of a generator or turbine). In someembodiments, the In Situ Control Mechanism(s) 106 may operate (e.g.,individually, in concert with each other, and/or under the control of acontroller) to improve gas extraction efficiency and/or to control theextraction process for a variety of desired outcomes including thedelivery of the extracted gas into a natural gas pipeline system. Insome embodiments the controller may be located remote from the In SituControl Mechanisms. (Such a remotely located controller is not shown inFIG. 1, but is shown in FIG. 5 and discussed below.)

It should be appreciated that an In Situ Control Mechanism, as describedherein, may control one or more parameters associated with a well, butis not a requirement that all other In Situ Control Mechanism bephysically located at that well. The In Situ Control Mechanism(s) may bedisposed at any suitable location(s). In some embodiments, each In SituControl Mechanism may be coupled to a single, corresponding well. Insome embodiments, an In Situ Control Mechanism may be coupled to one ormore wells. In some embodiments, some or all of the gas extraction wellsin a landfill gas extraction system may be outfitted with an In SituControl Mechanism 106, as depicted in FIG. 1. In some embodiments, an InSitu Control Mechanism 106 may be positioned at or adjacent to one ormore junction points in the gas extraction piping system 108 (headerjunctions, or leachate junctions, or others) to control the performanceof an entire section of piping. In some embodiments, an In Situ ControlMechanism 106 may be positioned between the gas extraction well 102 andthe gas collection system 110 such that gas coming from the well flowsthrough the In Situ Control Mechanism 106 on its way to the rest of thecollection system. The In Situ Control Mechanism 106 may be installedpermanently in a suitable location (e.g., in, on, adjacent to, and/ornear a well and/or gas extraction piping), or may be moved from locationto location (e.g., well to well) over time.

A block diagram of some embodiments of an In Situ Control Mechanism 200is presented in FIG. 2. In some embodiments, an In Situ ControlMechanism may include one or more mechanisms configured to control theflow of landfill gas from one or more wells to gas collection system 110through gas extraction piping system 108. Any suitable flow-controlmechanism 206 may be used, including, without limitation, a valve (e.g.,a solenoid valve, latching solenoid valve, pinch valve, ball valve,butterfly valve, ceramic disc valve, check valves, choke valves,diaphragm valves, gate valves, globe valves, knife valves, needlevalves, pinch valve, piston valve, plug valve, poppet valve, spoolvalve, thermal expansion valve, pressure reducing valve, sampling valve,safety valve) and/or any other suitable type of flow-control mechanism.

In some embodiments, an In Situ Control Mechanism may include one ormore actuation devices configured to control operation of the one ormore flow-control mechanisms (e.g., to open a flow-control mechanism,close a flow-control mechanism, and/or adjust a setting of aflow-control mechanism). In some embodiments, an In Situ ControlMechanism may include a controller 204 configured to determine thesettings to be applied to the one or more flow-control mechanisms (e.g.,via the actuation devices), and/or configured to apply the settings tothe one or more flow-control mechanisms (e.g., via the actuationdevices). In some embodiments, the settings to be applied to the one ormore flow-control mechanisms (e.g., via the actuation devices) may bedetermined remotely and communicated to the In Situ Control Mechanism(e.g., by a remotely located controller) using any suitablecommunication technique, including, without limitation, wirelesscommunication, wired communication, and/or power line communication.

In some embodiments, an In Situ Control Mechanism may include one ormore sensor devices configured to sense one or more attributesassociated with the landfill, including, without limitation, attributesof the landfill, attributes of the landfill gas, attributes of an areaadjacent to the landfill, and/or attributes of the landfill's gasextraction system. In some embodiments, the In Situ Control Mechanismmay include one or more actuation devices configured to controloperation of the one or more sensor devices (e.g., to activate a sensordevice, deactivate a sensor device, and/or collect data from the sensordevice). In some embodiments, an In Situ Control Mechanism may include acontroller 204 configured to determine the settings (e.g., controlsignals) to be applied to the one or more actuation and/or sensordevices, configured to apply the settings to the one or more actuationand/or sensor devices, and/or configured to collect data (e.g.,measurements) obtained by the one or more sensor devices. In someembodiments, the settings to be applied to the one or more actuationand/or sensor devices may be determined remotely and communicated to theIn Situ Control Mechanism (e.g., by a remotely located controller) usingany suitable communication technique, including, without limitation,wireless communication, wired communication, and/or power linecommunication. In some embodiments, the In Situ Control Mechanism maycommunicate the one or more sensed attributes associated with thelandfill (e.g., to a remotely located controller).

In some embodiments, the one or more sensor devices may include a GasAnalyzer 202. In some embodiments, a Gas Analyzer 202 may collect asample of landfill gas from the gas extraction piping 208 through aninput port 210, determine (e.g., compute, measure and/or sense) one ormore characteristics of that gas, and/or report the one or morecharacteristics of the gas to a controller (e.g., local controller 204and/or a remotely located controller). In some embodiments, the GasAnalyzer may determine the gas temperature, pressure, flow rate,humidity, energy content (e.g., energy density), gas composition(partial pressure or concentration of methane, oxygen, carbon dioxide,carbon monoxide, hydrogen sulfide, nitrogen and/or any other suitablegas) and/or any other characteristics of the landfill gas coming fromthe gas extraction well(s) upstream from the location where the In SituControl Mechanism is installed.

Accordingly, in some embodiments, Gas Analyzer 202 may include sensors205 configured to make such measurements. Sensors 205 may be of anysuitable type. In some embodiments, sensors 205 may include a sensorconfigured to detect partial pressure and/or concentration of methane inlandfill gas, a sensor configured to detect partial pressure and/orconcentration of oxygen in landfill gas, a sensor configured to detectpartial pressure and/or concentration of carbon dioxide in landfill gas,a sensor configured to detect partial pressure and/or concentration ofcarbon monoxide in landfill gas, a sensor configured to detect partialpressure and/or concentration of hydrogen sulfide in landfill gas, asensor configured to detect partial pressure and/or concentration ofnitrogen in landfill gas, and/or a sensor to detect partial pressure orconcentration of any suitable gas in landfill gas.

In some embodiments, sensors 205 may include one or more non-dispersiveinfrared (NDIR) sensors, mid infrared optical sensors, catalytic beads,electrochemical sensors, pellistors, photoionization detectors,zirconium oxide sensors, thermal conductivity detectors, and/or anyother sensing technology. Gas Analyzer 202 may be configured to measureflow rate by using one or more sensors 205 to determine a pressuredifferential across a venturi, orifice plate, or other restriction tothe flow of gas; by pitot tube, mechanical flow meter, heated wire orthermal mass flow meter, and/or using any other suitable technique. GasAnalyzer 202 may be configured to measure temperature with athermocouple, a negative or positive temperature coefficient resistor,capacitor, inductor, a semiconducting device, and/or using any othersuitable technique.

In some embodiments, one or more external sensors 203 may be used tomeasure one or more characteristics of the ambient environment outsideof Gas Analyzer 202 (e.g., outside of In Situ Control Mechanism 200).The external sensor(s) 203 may provide obtained measurements to In SituControl Mechanism 200 (e.g., to control 204) and/or to one or morecomputing devices located remotely from In Situ Control Mechanism 200(e.g., by using a wireless link, a wired link, and/or any suitablecombination of wireless and wired links). In some embodiments, externalsensor(s) 203 may include one or more temperature sensors configured tomeasure temperature outside the control mechanism 200 (e.g., the ambientatmospheric temperature) and/or any other suitable location. In someembodiments, external sensor(s) 203 may include one or more atmosphericpressure sensor(s) configured to measure atmospheric pressure outside ofthe control mechanism 200 (e.g., ambient atmospheric pressure) and/orany other suitable location. In some embodiments, sensors 203 may beused to measure one or more characteristics of the ambient environment.Additionally or alternatively, in some embodiments, information aboutthe characteristic(s) of the ambient environment may be obtained from anexternal data source (e.g., external forecast data, National Oceanic andAtmospheric Administration (NOAA) data for temperature and/or barometricpressure).

In some embodiments, the gas characteristics may be sampled once in eachreading, or may be sampled many times and statistics about thedistribution of values may be determined. The gas characteristics may becontinuously determined, or they may be determined at discrete timeintervals. In some embodiments, the Gas Analyzer may analyze gas in themain flow of landfill gas (e.g., within gas extraction piping 208). Insome embodiments, the Gas Analyzer may draw a small sample of gas into aseparate chamber for analysis. In some embodiments, certain parameters(for example flow rate, pressure, temperature, humidity, and the like)may be measured in the main gas stream (e.g., may be measured by sensorsdisposed directly within extraction gas piping), and others may beanalyzed in a separate chamber.

In order to improve measurement accuracy, measurement resolution,measurement repeatability, sensor lifetime, and/or sensor reliability, asample of gas from the well may be pre-treated before analysis, whichpre-treatment may include heating, cooling, drying, and/or any othersuitable pre-treatment processing (e.g., through forced condensation,passing through a desiccant, or any other suitable technique), filteredto remove particles, filtered to remove contaminants or other chemicals,pressurized, de-pressurized, and/or otherwise treated before beinganalyzed. After analyzing and reporting gas characteristics (e.g., tolocal controller 204 and/or to a remotely located controller), the GasAnalyzer may purge the gas sample from the chamber and vent it to theatmosphere, or return it to the main gas flow. In some embodiments, theanalyzed gas sample may be purged prior to reporting the gascharacteristics to a controller.

One embodiment of a Gas Analyzer 300 utilizing pre-treatment mechanismsas described above is illustrated in FIG. 3. In the Gas Analyzer 300 ofFIG. 3 and other arrangements not explicitly described here, a smallsample of landfill gas may be taken into the Gas Analyzer through inputport 310 (e.g., from the main flow of landfill gas in gas extractionpiping 308 between the gas extraction well and the gas collectionsystem) and sent through a drying element 312 and a series of one ormore flow-control mechanisms (e.g., valves) before entering the gasanalysis sample chamber 302. In some embodiments, at the beginning andend of a gas measurement cycle, both valves 316 and 318 are in theclosed state. Valve 316 may be opened and the pump 314 may be turned onin order to draw a sample of landfill gas through the drying element 312and into the gas analysis sample chamber 302 for analysis. At the end ofa measurement cycle, the pump 314 may be turned off and valve 316 may beclosed to stop the flow of gas into the sample chamber 302. In someembodiments, the gas sample may be purged from sample chamber 302 byopening valve 318. Under typical operating conditions, the gascollection system and gas extraction well(s) may be at negative pressure(i.e., operating under vacuum conditions) relative to atmosphericpressure, such that opening valve 318 may pull ambient air through theGas Analyzer 300 to purge the sample chamber 302 of landfill gas. Insome embodiments, one or more valves of Gas Analyzer 300 may be toggledand a pump (e.g., pump 314) may be activated to force purge samplechamber 302 with ambient air. Forced purging may be beneficial when oneor more wells upstream from Gas Analyzer 300 are operating underpositive pressure relative to atmospheric pressure (e.g., because thegas extraction system's vacuum is off-line or because the one or morewells are under-extracted). For example, forced purging may be aneffective technique for clearing condensate from the Gas Analyzer'stubes and/or for clearing sample gas from sample chamber 302 in caseswhere the upstream well(s) are operating under positive pressure.(Although not shown, one of ordinary skill in the art would understandthat a valve may be placed between pump 314 and input port 310, and thatsample chamber 302 may be force purged by closing this valve and byopening valves between pump 314 and atmospheric port 320.) After purgingthe gas sample from Gas Analyzer 300, valve 318 may be closed to stopatmospheric air from leaking into the gas collection system.

Configurations that perform a similar function to the embodiment of FIG.3 and which, while not described explicitly here, are within the scopeof the present disclosure. For example, the pump 314 may be placed aftervalve 316, or after the gas analyzer sample chamber 302, or the dryingelement 312 may be moved to a different point in the flow path.Similarly, the functionality provided by valve 316 and the pump 315 maybe consolidated by the use of a sealed pump design (e.g., a peristalticpump). An additional valve may be added after the gas analyzer (e.g., ina port 322 coupling the sample chamber 302 to the gas extraction piping308), for additional control or to prevent backflow into the samplechamber. Additionally, the Gas Analyzer may be outfitted with additionalmodules to provide other pre-treatment of the gas in addition to or inalternative to drying (for example, particle filtering, removal ordeactivation of hydrogen sulfide or other chemicals, etc.).

In some embodiments, the flow-control mechanism(s) of Gas Analyzer 300may include solenoid valves, latching solenoid valves, pinch valves,ball valves, butterfly valves, ceramic disc valves, check valves, chokevalves, diaphragm valves, gate valves, globe valves, knife valves,needle valves, pinch valves, piston valves, plug valves, poppet valves,spool valves, thermal expansion valves, pressure reducing valves,sampling valves, safety valves, and/or any other type of flow-controlmechanism.

In some embodiments, the Gas Analyzer may utilize non-dispersiveinfrared (NDIR) sensors, catalytic beads, electrochemical sensors,pellistors, photoionization detectors, zirconium oxide sensors, thermalconductivity detectors, and/or any other sensing technology. Flow ratemay be measured by a pressure differential across a venturi, orificeplate, or other restriction to the flow of gas; by pitot tube,mechanical flow meter, heated wire or thermal mass flow meter, and/orusing any other suitable technique. Temperature may be measured with athermocouple, a negative or positive temperature coefficient resistor,capacitor, inductor, a semiconducting device, and/or using any othersuitable technique. Temperature may be measured inside the well, in themain gas flow from the well to the collection system, inside a samplingchamber, outside of the control mechanism (e.g., ambient atmospherictemperature), and/or at any other suitable point. Atmospheric pressuremay be measured outside of the control mechanism (e.g., ambientatmospheric pressure) and/or at any other suitable location.Temperature, pressure, gas composition, and/or other readings fromdifferent points within the gas extraction well, the In Situ ControlMechanism, and/or the gas collection system may be used in conjunctionwith each other to obtain a more complete analysis of the operatingstate of the landfill gas collection system.

FIG. 4 shows a controller of an In Situ Control Mechanism, according tosome embodiments. In some embodiments, the Controller 400 of an In SituControl Mechanism may include functional blocks as indicated in FIG. 4.In the embodiment of FIG. 4, the Controller 400 includes a SignalProcessing Module 418, a Data Storage Device 420, a Real Time ClockModule 422, a Wireless Communication Module 416, and/or a Flow-ControlMechanism Actuator 412 (e.g., valve drive buffer) for providing acontrol signal to the Flow-Control Mechanism 406. Other embodiments mayuse only parts of this implementation, while others may add additionalfunctional modules for supporting functions. For example, in someembodiments, the Controller of an In Situ Control Mechanism may beimplemented using a one or more processors as described below.

In some embodiments, the Controller 400 of the In Situ Control Mechanismmay use data about environmental conditions in and around the landfill(e.g., in and around the gas extraction well upon which the In SituControl Mechanism is installed) to determine the settings to be appliedto the flow-control mechanism. In some embodiments, a remotely-locatedcontroller may use the environmental data to determine the settings tobe applied to the flow-control mechanism, and may communicate thosesettings to the In Situ Control Mechanism. The environmental data mayinclude information about parameters including, but not limited toatmospheric pressure, ambient temperature, wind direction, wind speed,precipitation, and/or any other suitable environmental parameter. The InSitu Control Mechanism may use information from one or more othersensors placed in or around the gas extraction well, including, withoutlimitation, atmospheric pressure sensor(s) (sometimes termed barometricpressure sensor(s), subsurface temperature probe(s), subsurface moistureprobe(s), collection well liquid level measurement sensors, measurementsof the chemical and/or biological processes (for example, pHmeasurements, tests for the presence of other chemicals or biologicalby-products, etc.) occurring in the section of waste that is in thevicinity of the gas extraction well, and/or any other suitableinformation. In embodiments, where one or more atmospheric pressuresensors are used, the atmospheric pressure sensors may be of anysuitable type, as aspects of the technology described herein are notlimited in this respect.

In some embodiments, the Controller 400 of the In Situ Control Mechanismmay use the current data about the gas characteristics and/orenvironmental parameters, and/or it may incorporate historical dataabout the performance of the gas extraction well to determine thesettings to be applied to the Flow-Control Mechanism. In someembodiments, a remotely-located controller may use the gas data,environmental data, and/or historical data to determine the settings tobe applied to the flow-control mechanism, and may communicate thosesettings to the In Situ Control Mechanism. The In Situ Control Mechanismmay, in some embodiments, incorporate past and/or present data about gasproduction into one or more predictive models and may use the predictivemodel(s) to determine the modulation of the Flow-Control Mechanismstate.

In some embodiments, the Signal Processing Module 418 takes gascharacteristics data from the Gas Analyzer 402 and converts it into aform that can be interpreted by the Computing Core 414. This may involvea interpreting a serial digital data stream via a serial parsingalgorithm, a parallel parsing algorithm, analog signal processing (forexample, performing functions on analog signals like filtering, addingor removing gain, frequency shifting, adding or removing offsets, mixingor modulating, and the like), digital signal processing (digitalfiltering, convolution, frequency shifting, mixing, modulating, and thelike), analog-to-digital or digital-to analog conversion, and/or anyother suitable signal processing technique that will be recognized byone of ordinary skill in the art.

In some embodiments, the Data Storage Device 420 may include anyvolatile and/or non-volatile memory element, including but not limitedto flash memory, SD card, micro SD card, USB drive, SRAM, DRAM, RDRAM,disk drive, cassette drive, floppy disk, cloud storage backup, and/orany other suitable computer-readable storage medium. The Data StorageDevice may serve as a data recovery backup, or it may hold data fortemporary intervals during the calculation of control signals. The DataStorage Device may be removable, or it may be fixed.

In some embodiments, the Real Time Clock Module 400 may include anycircuit and/or functional module that allows the Computing Core toassociate the results of a gas analyzer reading with a date or time(e.g., a unique date or time stamp).

In some embodiments, the Wireless Communication Module 416 may include,but is not limited to: a radio transceiver (AM or FM, or any othertype), television, UHF, or VHF transceiver, Wi-Fi and/or other 2.4 GHzcommunication module, cellular chipset (2G, 3G, 4G, LTE, GSM, CDMA,etc.), GPS transmitter, satellite communication system, and/or any othersuitable wireless communication device. The Wireless CommunicationModule may have an integrated antenna, and/or an external one. TheWireless Communication Module may transmit, receive, and/or have two-waycommunication with a central source and/or be capable of point-to-pointcommunication with another module. In some embodiments, the WirelessCommunication Module may include a 2G chipset that allows the In SituControl Mechanism to connect to existing telecommunicationsinfrastructure.

In some embodiments, the Computing Core 414 may include, but is notlimited to: a microprocessor, a computer, a microcontroller, a fieldprogrammable gate array (FPGA), an application specific integratedcircuit (ASIC), a digital signal processor (DSP), an analog computer orcontrol system, and/or any other suitable computing device. In someembodiments, the Computing Core may have integrated Analog-to-Digitalconverters, pulse width modulation detectors, edge detectors, frequencydetectors, phase detectors, amplitude detectors, demodulators, RMS-DCconverters, rectifiers, and/or other suitable signal processing modules.

In some embodiments, the Flow-Control Mechanism Actuator 412 (e.g., avalve drive buffer) may include any circuit that can translate commandsfrom the Computing Core into an appropriate actuation signal (e.g.,driving signal) for the Flow-Control Mechanism 406. In some embodiments,translating commands from the Computing Core may comprise analog signalprocessing on a voltage (for example, adding/removing gain, offset,filtering, mixing, etc.), analog signal processing on a current control(for example, conversion to a 4-20 mA control loop, increasing outputcurrent drive capability), pulse width modulating a digital signal,digital signal processing, digital-to-analog or analog-to-digitalconversion, and/or any other suitable techniques.

In some embodiments, the Flow-Control Mechanism 406 of the In SituControl Mechanism may comprise a solenoid valve, latching solenoidvalve, pinch valve, ball valve, butterfly valve, ceramic disc valve,check valve, choke valve, diaphragm valve, gate valve, globe valve,knife valve, needle valve, pinch valve, piston valve, plug valve, poppetvalve, spool valve, thermal expansion valve, pressure reducing valve,sampling valve, safety valve, and/or any other suitable type offlow-control mechanism. The Flow-Control Mechanism may have two or morediscrete operating states, or it may provide continuous adjustment ofthe operating state (e.g., valve position) for fine control of operatingpressure, temperature, flow, gas characteristics, etc.

In some embodiments, the In-Situ Control Mechanism may modulate theFlow-Control Mechanism to achieve any number of desired outcomes, or itmay determine the state of the Flow-Control Mechanism based on anoptimization and/or prioritization of multiple output parameters. Someexamples of control schemes might include, but are not limited to:

-   -   Modulation of the flow-control mechanism to maintain and/or        obtain a constant vacuum pressure in the gas extraction well (in        spite of varying atmospheric pressure, temperature, and/or        varying rates of gas generation, etc.);    -   Modulation of the flow-control mechanism to maintain and/or        obtain a constant flow rate of landfill gas from the extraction        well;    -   Modulation of the flow-control mechanism to control the flow        rate of landfill gas from the extraction well;    -   Modulation of the flow-control mechanism to maintain and/or        obtain a constant percentage of any of the constituent gases        (including but not limited to methane, carbon dioxide, oxygen,        nitrogen, etc.) in the landfill gas coming from the extraction        well;    -   Modulation of the flow-control mechanism to control (e.g.,        increase or decrease) the concentration of any of the        constituent gases in the landfill gas coming from the extraction        well;    -   Modulation of the flow-control mechanism to control (e.g.,        increase and/or decrease) the energy content of the landfill gas        (e.g., increase the total quantity of methane extracted in a        given period of time, etc.) coming from the extraction well;    -   Modulation of the flow-control mechanism to control the total        volume of the landfill gas (e.g., increase the total quantity of        landfill gas extracted in a given period of time, etc.) coming        from the extraction well;    -   Modulation of the flow-control mechanism to increase the rate of        extraction during periods of increased energy demand (e.g.,        increasing generation during the peaks of real time, hourly,        daily, weekly, monthly, or seasonal electricity prices);    -   Modulation of the flow-control mechanism to decrease the rate of        extraction during periods of reduced energy demand (e.g.,        reducing generation during the lows of real time, hourly, daily,        weekly, monthly, or seasonal electricity prices);    -   Modulation of the flow-control mechanism to control (e.g.,        maintain, improve, and/or establish) the long term stability of        the biochemical decomposition processes (aerobic or anaerobic        digestion, etc.) occurring within the section of waste that is        in the vicinity of the gas extraction well;    -   Modulation of the flow-control mechanism to control (e.g.,        increase and/or decrease) the rates of decomposition occurring        within the section of waste that is in the vicinity of the gas        extraction well;    -   Modulation of the flow-control mechanism to match the operating        parameters or limitations of the gas collection system;    -   Modulation of the flow-control mechanism to prevent or        extinguish underground fires or other potentially dangerous        events occurring within the section of waste that is in the        vicinity of the gas extraction well;    -   Modulation of the flow-control mechanism to mitigate emission of        odors;    -   Modulation of the flow-control mechanism to control (e.g.,        reduce) emissions of landfill gas or components of landfill gas        (H₂S, methane, etc.) in the vicinity of the gas extraction        wells;    -   Modulation of the flow-control mechanism to control (e.g.,        reduce) gas losses into the atmosphere;    -   Modulation of the flow-control mechanism to control (e.g.,        maintain, improve, and/or establish) compliance of the gas        extraction system with local, state and/or federal regulations;        and/or    -   Modulation of the flow-control mechanism to reduce damage to an        engine, turbine, or other energy generation equipment from        contaminants emanating from the vicinity of a gas extraction        well.

In some embodiments, some or all of the gas extraction wells and/orpiping junction points in a landfill may be outfitted with In-SituControl Mechanisms to form at least a portion of a control system forcontrolling gas extraction across the entire landfill or a set of wellswithin the landfill (the “landfill under control”). One embodiment ofsuch a control system is shown in FIG. 5.

FIG. 5 shows a control system 500 for a landfill gas extraction system,according to some embodiments. In some embodiments, control system 500may include one or more In Situ Control Mechanisms 506 configured tocontrol gas flow in a gas extraction system in a landfill under control520. In some embodiments, control system 500 may include a controllermodule 504 for modeling aspects of the landfill under control, forcommunicating with the In Situ Control Mechanisms, and/or forcontrolling the operation of the In Situ Control mechanisms. In someembodiments, controller module 504 may be implemented on one or morecomputers located remotely from the In Situ Control Mechanisms (e.g., ona centralized computer or in a distributed computing environment). Insome embodiments, controller module 504 may execute a multitaskingprogram with different tasks configured to control the operation ofdifferent In Situ Control Mechanisms and/or to communicate withdifferent In Situ Control Mechanisms. In some embodiments, thefunctionality described below as being performed by controller module504 may be performed by one or more In Situ Control Mechanisms 506individually or in concert. In some embodiments, controller module 504may communicate with the In Situ Control Mechanisms through a devicemanager 502. In some embodiments, controller module 504 be incommunication with a user interface 508 and/or a database 510.

In some embodiments, some or all of these In-Situ Control Mechanisms 506may contain wireless communication capability to establish Wireless DataLinks to controller module 504 (e.g., through device manager 502).Wireless Data Links may operate in either a unidirectional or abidirectional manner. The network of Wireless Data Links may beimplemented using a mesh network, a star network, point-to-pointcommunication, and/or any other suitable communication technique.In-Situ Control Mechanisms 506 may send information over a communicationnetwork to a distributed network (e.g., the “cloud”). Communication mayoccur through a system including but not limited to a cell phone network(2G, 3G, 4G LTE, GSM, CDMA 1×RTT, etc.), a satellite network, a localarea network connected to the Internet, etc. In some embodiments, the InSitu Control Mechanisms 506 may communicate with each other and/or withcontroller module 504 using wired data links, Wireless Data Links, powerline communication, and/or any other suitable communication technique.

Information sent (e.g., over Wireless Data Links) by the In-Situ ControlMechanisms 506 may include but is not limited to sensor data,environmental data, failure notifications, status notifications,calibration notifications, etc. Information received by the In-SituControl Mechanisms may include but is not limited to: raw orpre-processed data about the current or past operational state of otherlandfill gas extraction wells in the landfill under control, command andcontrol signals, desired operating states, predictive calculations aboutthe operating state of the well upon which the In-Situ Control Mechanismis installed or other landfill gas extraction wells, failurenotifications, status notifications, calibration changes, softwareand/or firmware updates, flow-control mechanism settings, sensorsettings, and/or other information.

In some embodiments, In Situ Control Mechanisms 506 in the landfillunder control 520 may communicate with a Device Manager 502, asindicated in FIG. 5, and/or they may communicate directly with eachother. The Device Manager 502 may include software operating on acomputer in the landfill under control, or operating on a remote server,and/or operating on a distributed computing network (“the cloud”) in oneor multiple locations. In some embodiments, Device Manager 502 may beimplemented using a computing system 1100 as described below. The DeviceManager 502 may collect information from alternate sources—including butnot limited to environmental data, past history about electrical powerdemand and/or prices, forecasts about future electrical power demandand/or prices, etc. In some embodiments, the Device Manager 502 may bein constant communication with the In-Situ Control Mechanisms 506, or itmay communicate asynchronously with the In-Situ Control Mechanisms. Insome embodiments, the Device Manager 502 may hold a queue of commands orother information to be passed to the In Situ Control Mechanism(s) 506upon the establishment of a data link (e.g., re-establishment of aWireless Data Link).

In some embodiments, the Device Manager 502 may associate a set ofIn-Situ Control Mechanisms 506 into a single landfill under control 520,and it may add or remove additional In-Situ Control Mechanisms 506 tothat landfill under control 520 to accommodate the addition or removalof In-Situ Control Mechanisms from the site. The Device Manager 502 maycontain or perform authentication or encryption procedures uponestablishing a data link (e.g., a Wireless Data Link) with an In-SituControl Mechanism. Security protocols implemented by the Device Managermay include, but are not limited to: internet key exchange, IPsec,Kerberos, point to point protocols, transport layer security (TLS),HTTPS, SSH, SHTP, etc.

In some embodiments, the Device Manager 502 may communicate with acontroller module 504. The controller module 504 may include one or moreapplications running on a distributed computational platform (e.g., a“cloud server”), a traditional server infrastructure, a computing system1100 as described below, and/or other suitable computer architecturerecognized by those of ordinary skill in the art. It should beappreciated, however, that control functions as described herein may bedistributed across device manager 502, controller module 504 and/or anyother computing components in any suitable way. Similarly, controlfunctions may be distributed across processors (e.g., controllers)associated with one or more In Situ Control Mechanisms.

In some embodiments, control system 500 may be configured to predictfuture states of the landfill under control, and/or may be configured touse such predictions to control the operation of a gas extraction systemassociated with the landfill under control. In some embodiments, usingone or more predictions regarding the future state(s) of the landfillunder control to control the operation of the gas extraction system mayimprove the performance (e.g., efficiency) of the gas extraction system,relative to the performance of conventional gas extraction systems.

FIG. 6 shows a feedback-based, predictive control system 600, which maybe implemented by some embodiments of control system 500 to control theoperation of gas extraction system associated with a landfill undercontrol 620. Feedback-based, predictive control system 600 may include apredictive landfill state estimator 602 for predicting one or morefuture states of a landfill under control 620, and one or more controlmodules 605 for controlling the operation of a gas extraction system(e.g., by controlling the operation of one or more in situ controlmechanisms 606 in the landfill under control 620) based, at least inpart, on the predicted future state(s) of the landfill under control620. The predictive landfill state estimator 602 and/or controlmodule(s) 605 may be implemented by controller 504 and/or bycontroller(s) 204 of in situ control mechanism(s) 606, with thefunctions of the predictive landfill state estimator 602 and the controlmodule(s) 605 being divided among the controller 504 and the in situcontrol mechanism(s) 606 in any suitable way.

In some embodiments, predictive landfill state estimator 602 may includeone or more predictive models of the landfill under control 620. Eachmodel may relate a set of parameters defining a current state of thelandfill to one or more sets of parameters, defining one or more futurestates of the landfill. Any suitable modeling techniques may be used todevelop such a model, which may be implemented using softwareprogramming on a computing device. Different models may be selecteddepending on parameters defining input or output states. For example,different models may be used to predict parameters such as odor, energyproduction, or gas production.

In some embodiments, predictive landfill state estimator 602 may use apredictive model to predict a future state 638 of at least one attributeof a landfill under control, based on a model of the landfill undercontrol and/or based on suitable input data. In some embodiments, thepredictive landfill state estimator 602 may apply mathematical models topresent and/or past data about the landfill under control 620 (e.g.,data about landfill gas production and/or extraction) to estimate afuture state of the landfill under control (e.g., the future LFGproduction and/or extraction). Suitable input data for the predictivelandfill state estimator 602 may include the current state 634 offlow-control mechanisms in the gas extraction system of the landfillunder control (e.g., the operating states of valves in the gasextraction system), the current state 635 of the landfill under control(e.g., the characteristics of the landfill's gas, as determined usingthe in situ control mechanism's sensors), and/or environmental data 636(e.g., data describing environmental conditions in and/or around thelandfill, as determined by the in situ control mechanism's sensors orany other suitable data source). In some embodiments, the predictedfuture state may correspond to a specified date and/or time in thefuture.

In some embodiments, control module(s) 605 may control the operation ofthe gas extraction system based, at least in part, on the predictedfuture state 638 of the landfill under control. For example, controlmodule(s) 605 may determine the values of control parameters 644(“control settings”) for the in situ control mechanism(s) 606 based onthe predicted future state 638. In embodiments where the controlmodule(s) are not implemented by the in situ control mechanism(s) 606,the control module(s) may send the determined values of the controlparameters 644 to the in situ control mechanism(s) 606. The in situcontrol mechanism(s) 606 may apply the control parameters toflow-control mechanisms in the gas extraction system (e.g., valves) tocontrol the operation of the gas extraction system (e.g., the in situcontrol mechanism(s) 606 may adjust the gas extraction rate from thelandfill under control 620 by modulating the positions of valves in thegas extraction system). As another example, control module(s) 605 maydetermine changes in the current values of control parameters 644 forthe in situ control mechanisms(s) 606 based on the predicted futurestate, and the in situ control mechanism(s) may change the controlparameters of the flow-control mechanisms by the determined amounts.

In some embodiments, control module(s) 605 may determine the values (orchanges in the values) of the control parameters 644 based on predictedfuture state 638 and/or based on other input data. For example, controlmodule(s) 605 may determine a difference between a predicted and adesired future state, determine control parameters 644 to reduce thatdifference, and apply the control parameters to in situ controlmechanism(s) 606 (e.g., by controlling an in situ control mechanism toadjust a valve or other actuator in accordance with the controlparameters) to reduce that difference. The input data may include thecurrent state 634 of flow-control mechanisms in the gas extractionsystem, the current state 635 of the landfill under control, designconstraints 640, and/or set point(s) 642.

In some embodiments, design constraints 640 may include physicallimitations of the landfill gas extraction system including, but notlimited to: operating ranges of the flow-control mechanisms (e.g.,available valve movement range), accuracy of the operating states of theflow-control mechanisms (e.g., valve position accuracy), resolution ofthe operating states of the flow-control mechanisms (e.g., valveposition resolution), gas extraction system vacuum pressure, measurementranges of the in situ control mechanism(s)' sensors, power generationcapacity at a landfill gas to energy power plant, total flow raterestrictions of the landfill gas extraction system, and/or any othersuitable limitations. In some embodiments, design constraints 640 may behard-coded values, and/or they may be specific to particular well,collection of wells, landfills, or geographic regions. In someembodiments, design constraints may be re-programmed by a human operatorthrough a software or hardware interface (for example, a webapplication, a mobile application, through manual or over the airfirmware upgrades, etc.). Control module 605 may use these designconstraints, for example, in selecting values of control parameters suchthat the design constraints are not violated.

In some embodiments, the set point(s) 642 may indicate a desiredoperating state for the gas extraction system (e.g., an energy contentextraction rate, gas flow rate, gas composition, and/or other suitablecharacteristic for the gas extraction system, for individual wells,and/or for individual in situ control mechanisms). In some embodiments,the control module(s) 605 may determine the values of the controlparameters 644 (e.g., using a mathematical model or models) to maintainthe state of the landfill under control equal to, less than, or greaterthan the set point. In this manner, the control module(s) 605 may usethe state of the landfill (e.g., the current and/or predicted states ofthe landfill) to control the gas extraction system to operate in adesired operating state (as indicated by the set point(s)), withoutviolating the system's design constraints. The set point(s) may be hardcoded into the system, may be user adjustable via a software interface(e.g., web or mobile application), and/or may be set and/or adjustedusing any other suitable technique.

Predictive landfill state estimator 602 may obtain its input data usingany suitable technique. In some embodiments, predictive landfill stateestimator 602 may obtain the current state 634 of the flow-controlmechanisms in the gas extraction system and/or the current state 635 ofthe landfill from the in situ control mechanism(s) 606 (e.g., byquerying the in situ control mechanism(s) 606 via the Device Manager).

FIG. 7 shows a feedback-based, predictive control system 700, which maybe implemented by some embodiments of control system 500 to control theoperation of gas extraction system associated with a landfill undercontrol 620. In some embodiments, feedback-based, predictive controlsystem 700 may be adaptive (“self-learning”). In some embodiments of theadaptive control system 700, the predictive landfill state estimator 702may compare the current state 635 of the landfill (e.g., the currentstate of landfill gas production) to the previously predicted state 738of the landfill, and modify parameters in the state estimator's stateestimation model or models to make the predicted states more closelymatch the actual measured states. In this manner, the accuracy of thestate estimator's predictions may improve over time, and/or the stateestimator may adapt to changing conditions over time, so that the stateestimator's predictions remain accurate even as the conditions in andaround the landfill change.

In some embodiments, adaptive control system 700 may include apredictive landfill state estimator 702, a state comparator 750, and amodel adapter 752. In some embodiments, predictive landfill stateestimator 702 may include one or more predictive models of the landfillunder control 620, and may apply the predictive model(s) to suitableinput data (e.g., current state 634 of flow-control mechanisms, currentstate 635 of the landfill under control, and/or environmental data 636)to predict one or more future states 738 of the landfill under control.

In some embodiments, state comparator 750 and model adapter 752 mayadapt the state estimator's predictive model(s) to improve the accuracyof the predictive model(s). In some embodiments, state comparator 750may compare a predicted future state 738 of the landfill and asubsequently measured current state 635 of the landfill. In someembodiments, model adapter 752 may use the difference 760 between thepredicted state and the actual state of the landfill to determinemodified parameter values 762 for one or more parameters in the stateestimator's predictive model(s), to improve (e.g., continually improve)the accuracy of those models.

In some embodiments, the modified parameter values 762 output by themodel adapter 752 may act to reduce the difference between the predictedfuture state of the landfill (if it were recalculated using the modifiedparameter values) and the actual current state of the landfill (e.g., toreduce the difference to zero). In some embodiments, the modifiedparameter values 762 may act to reduce (e.g., minimize) another errormetric (e.g., to reduce the mean error, the sum of the squares of errorsfor one or more (e.g., all) previous predictions, and/or any othermetric). The modified parameter values 762 may be output after everycycle of the feedback loop, or they may be selectively applied. In someembodiments, the model adapter 752 may detect anomalous data points inthe measured current state 635 of the landfill (as may happen, e.g.,during natural events (e.g., extreme weather), during equipmentmalfunction (e.g., sensor or control valve failures), when theoperations of the Landfill Gas to Energy plant are suddenly disrupted,etc.). In some embodiments, control system 700 may not apply modifiedparameter values 762 to the predictive model(s) of the predictivelandfill state estimator 702 during such events.

In some embodiments, adaptive control system 700 may also include one ormore control module(s) 605 and one or more in situ control mechanism(s)606, which may control the operation of a gas extraction systemassociated with landfill under control 620. Some embodiments of controlmodule(s) 605 and in situ control mechanism(s) 606 are described abovewith reference to FIG. 6. For brevity, these descriptions are notrepeated here.

Returning to the control system 500 shown in FIG. 5, in some embodimentsthe controller module 504 may be in communication with a database 510and/or a user interface 508. In some embodiments, the database 510 maybe implemented on a centralized storage mechanism (hard drive, diskdrive, or some other non-volatile memory), or it may reside on adistributed storage mechanism (e.g., a cloud server, or any othersuitable distributed storage device). The database 510 may serve as along term archive of historical data and/or past predictions from thepredictive landfill state estimator 602, and/or may store past designconstraints 640, current design constraints 640, past set points 642,current set points 642, any parameters from the state estimator'spredictive model(s), any parameters from the flow-control mechanisms,and/or any other data (for example, environmental data, data fromlandfill operations, etc.). In some embodiments, the data stored indatabase 510 may be used to train predictive landfill state estimator702. In some embodiments, the data stored in database 510 may beprovided as input data to the predictive landfill state estimator, whichmay use the data to predict the next state of the landfill undercontrol. In some embodiments, the data stored in database 510 may beprovided as input data to the control module(s) 605 and may be used todetermine the values of control parameters 644. The database may beimplemented using MySQL, dBASE, IBM DB2, LibreOffice Base, Oracle, SAP,Microsoft SQL Server, MariaDB, SQLite, FoxPro, and/or any othercommercially available database management software that will berecognized by one of ordinary skill in the art. In some embodiments, thedatabase may be of a custom construction.

In some embodiments, the controller module 504 may display certain dataand/or accept inputs via a user interface 508. In some embodiments, theuser interface 508 may include a web site, may include a mobileapplication (tablet, phone, or other mobile device), and/or may beprovided through a terminal via a local network (e.g., secure localnetwork) operating at the landfill under control. The user interface maydisplay current and/or historical gas extraction data collected from aparticular well or any set of wells in a given landfill. The userinterface may display data via tables, charts, graphs, and/or any othersuitable technique, and may do so over various periods of time (e.g.,the previous day, past week, past month, etc.). The user interface mayoverlay data from wells in a given landfill on top of or embedded intoaerial maps or renderings of the landfill, and/or it may display dataoverlays with topographical maps, schematics of the underground pipingsystem, and/or other engineering drawings.

In some embodiments, the user interface may allow users to click on aparticular well or set of wells and manually adjust set points, designconstraints, and/or other parameters of the control system 500 as theypertain to those wells. The user interface may allow users to set alarmsor notifications if gas extraction data or gas data from wells undercontrol cross certain thresholds as defined by the user (for example, auser may request an email or SMS message to be sent in the event thatgas from any well exceeds 55% methane or drops below 45% methane byvolume, and/or a user may set an alarm if gas temperature rises above120 degrees Fahrenheit at any well, etc.).

In some embodiments, control modules 605 corresponding to two or more InSitu Control Mechanisms 606 may be in communication with each other(e.g., control modules 605 may be implemented by controller 504 andshare data through the memory of controller 504, and/or control modules605 may be implemented by the corresponding In Situ Control Mechanisms,which may communicate with each other directly or through controller504). The control parameters 644 for a given In Situ Control Mechanism606 may then be determined in accordance with, and/or driven by, thebehavior, control parameters, sensor readings, and/or other data ofother In Situ Control Mechanisms in the landfill under control (e.g., inthe surrounding area). Such interdependence among the control parameters644 of the in situ control mechanisms 606 may improve the performance ofthe gas extraction system, because adjustments to each gas extractionpoint, being in fluid communication in the trash, and/or in fluidcommunication through the gas extraction piping system, may influencethe surrounding areas. The spatial area around a given landfill gasextraction well that is affected by that well is called its “Zone ofInfluence.”

FIG. 8 depicts the Zones of Influence around a set of several gasextraction wells 802 a-c. In this example, well 802 c has overlappingzones of influence 806 with both other wells. In such an example,changes to the gas extraction rate at well 802 c will impact the gascharacteristics at wells 802 a and 802 b. In some embodiments of thelandfill gas extraction control system disclosed herein, one objectiveof the processing performed by the state estimator and/or controlmodule(s) 605 may be to identify such overlapping zones of influence andincorporate interactions between wells into their models.

The inventors have recognized and appreciated that as the porosity ofwaste in a landfill varies (due to heterogeneous waste composition andcompaction at the time of dumping, and also due to the naturaldecomposition of waste over time and settling effects), certain wellsmay have highly irregular zones of influence 904 a-b as depicted in FIG.9 below. By placing a set of In-Situ Control Mechanisms on adjacentwells in a landfill, it may be possible to quantify and model thestrength of interactions between individual wells and to create aninteraction matrix that captures an effective “coupling parameter”between any two or more wells in that landfill. In some embodiments, thecoupling parameters and/or the interaction matrix may be used to developor improve the model(s) of the state estimator and/or control module(s)605 in the control system, and/or may be used to inform the placement ofadditional wells (e.g., in areas of the landfill where gas extractionmay be lacking with the existing wells).

The techniques and devices disclosed herein may be used to modulate therate of gas extraction of a well or set of wells in accordance with anysuitable control scheme, including but not limited to:

-   -   Modulation of the gas extraction rate to control vacuum pressure        (e.g., maintain and/or obtain a constant vacuum pressure) in the        landfill and/or wells under control (in spite of varying        atmospheric pressure, temperature, and/or varying rates of gas        generation, etc.);    -   Modulation of the gas extraction rate to maintain and/or obtain        a constant flow rate of landfill gas from the landfill and/or        wells under control;    -   Modulation of the gas extraction rate to control (e.g., increase        or decrease) the flow rate of landfill gas from the landfill        and/or wells under control;    -   Modulation of the gas extraction rate to maintain and/or obtain        a constant percentage of any of the constituent gases (including        but not limited to methane, carbon dioxide, oxygen, nitrogen,        etc.) in the landfill gas coming from the landfill and/or wells        under control;    -   Modulation of the gas extraction rate to control (e.g., increase        or decrease) the concentration of any of the constituent gases        in the landfill gas coming from the landfill or wells under        control;    -   Modulation of the gas extraction rate to control (e.g., increase        or decrease) the energy content of the landfill gas (e.g.,        control the total quantity of methane extracted in a given        period of time, etc.) coming from the landfill and/or wells        under control;    -   Modulation of the gas extraction rate to control (e.g., increase        or decrease) the total volume of the landfill gas (e.g., control        the total quantity of landfill gas extracted in a given period        of time, etc.) coming from the landfill and/or wells under        control;    -   Modulation of the gas extraction rate to increase the rate of        extraction during periods of increased energy demand (e.g.,        increasing generation during the peaks of real time, hourly,        daily, weekly, monthly, and/or seasonal electricity prices);    -   Modulation of the gas extraction rate to decrease the rate of        extraction during periods of reduced energy demand (e.g.,        reducing generation during the lows of real time, hourly, daily,        weekly, monthly, or seasonal electricity prices);    -   Modulation of the gas extraction rate to control (e.g.,        maintain, improve, and/or establish) the long term stability of        the biochemical decomposition processes (aerobic or anaerobic        digestion, etc.) occurring within a section of waste that is in        the vicinity of the well(s) under control;    -   Modulation of the gas extraction rate to control (e.g., increase        or decrease) the rates of decomposition occurring within a        section of waste that is in the vicinity of the well(s) under        control;    -   Modulation of the gas extraction rate to match the operating        parameters or limitations of the gas collection system for the        landfill and/or wells under control (including limitations of        header junctions and/or subsections of underground piping that        impact only certain wells);    -   Modulation of the gas extraction rate to prevent or extinguish        underground fires and/or other potentially dangerous events        occurring within a section of waste that is in the vicinity of        the well(s) under control;    -   Modulation of the gas extraction rate to control (e.g., reduce)        emission of odors from the landfill and/or wells under control;    -   Modulation of the gas extraction rate to control (e.g., reduce)        emissions of landfill gas or components of landfill gas (H₂S,        methane, etc.) in the vicinity of the gas extraction well(s)        under control;    -   Modulation of the gas extraction rate to control (e.g., reduce)        gas losses into the atmosphere;    -   Modulation of the gas extraction rate to control (e.g.,        maintain, improve, and/or establish) compliance of the gas        extraction system with local, state and/or federal regulations;    -   Modulation of the gas extraction rate to control (e.g., reduce)        damage to an engine, turbine, and/or other energy generation        equipment from contaminants emanating from the vicinity of a        well or wells under control;

The success or failure of the above-described control schemes may beassessed in any suitable way. In some embodiments, attributes of thelandfill gas may be monitored over a period of time, and a determinationmay be made as to whether the monitored values comply with the controlscheme. For example, to determine whether a specified quantity ofmethane has been extracted from the landfill in a specified time period,the concentration of methane in the extracted landfill gas and the flowrate of the extracted landfill gas may be monitored during the timeperiod, and quantity of extracted methane may be determined based on themonitored methane concentration levels and gas flow rates. In someembodiments, attributes of the landfill gas may be measured at aspecified time, and a determination may be made as to whether themeasured values comply with the control scheme. For example, todetermine whether the flow rate of extracted landfill gas matches atarget flow rate, the flow rate of extracted landfill gas may bemeasured at some time and compared to the target flow rate.

In some embodiments, the control system 500 may be used to monitor theeffect of other treatments besides just the setting of the control valve(e.g., monitoring effects of microbial treatment, leachaterecirculation, watering out/pumping of the wells, adding iron, H₂Sabatement, etc.).

FIG. 10 illustrates a method 1000 for control extraction of landfill gasfrom a landfill through a gas extraction system, according to someembodiments. In step 1002 of method 1000, values indicating conditionsassociated with the landfill are measured. In step 1004 of method 1000,a future state of the landfill is predicted based, at least in part, onthe measured values and on the model of the landfill. In someembodiments, the predicted future state may be computed by at least onecomputing device. In step 1006 of method 1000, one or more controlparameters are determined for one or more control devices configured tocontrol operation of the landfill's gas extraction system. In step 1008of method 1000, the control parameter(s) are applied to the controldevice(s) of the gas extraction system. In step 101 of method 1000,extraction of the landfill gas is controlled (e.g., by the one or morecontrol devices) based, at least in part, on the control parameter(s).

In some embodiments, the predicted future state of the landfill mayinclude one or more predicted attributes of the landfill gas produced bythe landfill and/or extracted by the gas extraction system at a futuretime and/or in a future time period. In some embodiments, the futurestate of the landfill may be predicted based, at least in part, on thepredicted future state of the landfill, on the model of the landfill, onthe current state of the landfill, on control parameter(s) applied tothe control device(s) before making the prediction, and/or onenvironmental data indicating environmental conditions associated withthe landfill. In some embodiments, the current state of the landfill mayinclude the measured values indicating conditions associated with thelandfill. In some embodiments, the measured values may be measured bysensor devices (e.g., sensor devices associated with one or more in situcontrol mechanisms). The values indicating conditions associated withthe landfill may include temperature, pressure, flow rate, humidity,energy content (e.g., energy density), and/or composition of thelandfill gas. In some embodiments, the determined attributes maycorrespond to landfill gas provided by a single well, landfill gasprovided by a plurality of wells, and/or landfill gas extracted from thelandfill. In some embodiments, the environmental data may indicateatmospheric pressure, ambient temperature, wind direction, wind speed,characteristics of ambient precipitation, subsurface temperature,subsurface moisture level, and/or pH value of an area of the landfill oradjacent to the landfill.

In some embodiments, the one or more control parameters may bedetermined based, at least in part, on predicted future electrical powerdemand and/or on an energy content of the landfill gas extracted fromthe landfill. In some embodiments, the one or more control parametersmay be applied to the one or more respective control devices in realtime. In some embodiments, controlling extraction of the landfill gasfrom the landfill may include controlling a flow rate and/or compositionof the landfill gas extracted from the landfill. In some embodiments,the control parameter(s) may be determined based, at least in part, onthe predicted future state of the landfill, on a current state of thelandfill, on one or more current values of the control parameters,and/or on a control objective for the landfill. In some embodiments, thecontrol parameter(s) may be determined based, at least in part, onelectrical power data including past electrical power consumption, pastelectrical power prices, predicted future electrical power demand,and/or predicted future electrical power prices. In some embodiments,the control parameter(s) may be determined based, at least in part, on atarget rate at which the landfill gas is extracted from the landfill bythe gas extraction system, a target vacuum pressure applied to the gasextraction system, a target composition of the landfill gas extractedfrom the landfill by the gas extraction system, a target energy contentof the landfill gas extracted from the landfill by the gas extractionsystem, a target volume of the landfill gas extracted from the landfillby the gas extraction system, a target stability of a decompositionprocess in the landfill, a target rate of a decomposition process in thelandfill, a target rate of emission of the landfill gas into anatmosphere, a target odor level associated with emission of the landfillgas into the atmosphere, and/or a target level of compliance with one ormore regulations applicable to the landfill. In some embodiments, thecontrol parameter(s) may be determined based, at least in part, on theexact chemical composition of the gas as specified by the operator ofthe pipeline system into which the extracted gas is being introduced.

Although not illustrated in FIG. 10, some embodiments of method 1000 mayinclude one or more steps for adapting the predictive model(s) of thepredictive landfill state estimator. In some embodiments, such steps mayinclude (1) after computing the predicted future state of the landfillat the future time, determining an actual state of the landfill at thefuture time, and (2) adapting the model based, at least in part, on adifference between the predicted future state of the landfill and thedetermined actual state of the landfill. In some embodiments, adaptingthe model may include adapting the model to decrease the differencebetween the predicted future state of the landfill and the determinedactual state of the landfill.

FIG. 12 is a flowchart of an illustrative process 1200 for controllingextraction of landfill gas through a gas extraction system, according tosome embodiments. Process 1200 may be performed by any suitable systemand, for example, may be performed by control system 500 describedherein with reference to FIG. 5. In some embodiments, the entirety ofprocess 1200 may be performed by an in situ controller and, for example,may be performed by in situ controller 400 described herein withreference to FIG. 4. In some embodiments, one or more acts of process1200 may be performed by an in situ controller (e.g., in situ controller400) co-located with a flow-control mechanism (e.g., a valve) and one ormore other acts of process 1200 may be performed by a remote controller(e.g., controller module 504).

Process 1200 may be used for controlling extraction of landfill gas suchthat the concentration(s) of one or more constituent gases fall within atarget range or ranges. For example, process 1200 may be used forcontrolling extraction of landfill gas such that the concentration ofmethane in the extracted landfill gas is in a specified range (e.g.,35%-65% by volume, 40%-60% by volume, 45-55% by volume, and/or any othersuitable target range within these ranges).

Process 1200 begins at act 1202, where a measured concentration of afirst gas is obtained. The measured concentration may be obtained byusing one or more sensors (e.g., one or more of sensors 205) configuredto sense partial pressure and/or concentration of the first gas in thelandfill gas being extracted from a landfill. The first gas may bemethane, oxygen, nitrogen, carbon dioxide, carbon monoxide, hydrogensulfide or any other gas that may be part of gas being extracted from alandfill.

Next, process 1200 proceeds to decision block 1204, where it isdetermined whether the measured concentration of the first gas obtainedat act 1202 is less than a first target threshold concentration. Forexample, the first gas may be methane and it may be determined, atdecision block 1204, whether the measured concentration of methane isless than a first target concentration of methane (e.g., less than 30%by volume, less than 35% by volume less than 40% by volume, less than45% by volume, less than 50% by volume, less than 55% by volume, and/orless than any suitable percentage in the 30-55% range by volume).

When it is determined that the measured concentration is less than thefirst threshold concentration, process 1200 proceeds, via the YESbranch, to act 1206, where one or more flow control mechanisms arecontrolled to reduce the flow rate of landfill gas being extracted fromthe landfill. For example, in some embodiments, a single flow controlmechanism (e.g., a valve) may be controlled to reduce the flow rate oflandfill gas (e.g., by closing the valve to a greater degree). In someembodiments, multiple flow control mechanisms (at a same site ordifferent sites in a landfill) may be controlled to reduce the flow rateof landfill gas. In some embodiments, a valve may be closed by apredefined increment, for example, by 5% or by any other suitableamount. In some embodiments, a flow control mechanism may be controlledby an in situ and/or a remote controller by receiving one or morecontrol signals from the in situ controller and/or the remotecontroller.

On the other hand, when it is determined that the measured concentrationis greater than or equal to the first threshold concentration, process1200 proceeds, via the NO branch, to decision block 1208, where it isdetermined whether the measured concentration obtained at act 1202 isgreater than a second target threshold concentration. For example, thefirst gas may be methane, and it may be determined, at decision block1208, whether the measured concentration of methane is greater than asecond target concentration of methane (e.g., greater than 40% byvolume, greater than 45% by volume, greater than 50% by volume, greaterthan 55% by volume, greater than 60% by volume, greater than 65% byvolume, and/or greater than any suitable percentage in the 40-70% rangeby volume).

When it is determined that the measured concentration is not greaterthan the second target threshold concentration, process 1200 completes,as the measured concentration is in the target range (between the firstand second target concentrations). The process 1200 may be repeatedperiodically and/or according to a schedule to continue monitoring theconcentration of the first gas in the landfill gas being extracted fromthe landfill.

On the other hand, when it is determined, at decision block 1208, thatthe measured concentration is greater than the second thresholdconcentration, process 1200 proceeds, via the YES branch, to act 1210,where one or more flow control mechanisms are controlled to increase theflow rate of landfill gas being extracted from the landfill. Forexample, in some embodiments, a single flow control mechanism (e.g., avalve) may be controlled to increase the flow rate of landfill gas(e.g., by opening the valve to a greater degree). In some embodiments,multiple flow control mechanisms (at a same site or different sites in alandfill) may be controlled to increase the flow rate of landfill gas.In some embodiments, a valve may be opened by a predefined increment,for example, by 5% or by any other suitable amount.

As shown in FIG. 12, after completion of either of acts 1206 and 1208,process 1200 returns to act 1202, where an updated measurement of theconcentration of the first gas may be obtained and another iteration ofthe process 1200 may begin to be performed. In this way, process 1200may involve iteratively increasing and/or decreasing the flow rate ofgas (e.g., by opening and/or closing one or more valves) in order toachieve a target concentration of a constituent gas.

It should be appreciated that process 1200 is illustrative and thatthere are variations. For example, although the control schemeillustrated in FIG. 12 may be used for achieving a target concentrationof methane in landfill gas, the relationship between flow rate and gasconcentration for other gasses (e.g. oxygen and nitrogen) may bedifferent. Accordingly, in some embodiments, when the first gas isoxygen or nitrogen, one or more flow control mechanisms may becontrolled to increase (rather than decrease as the case may be when thefirst gas is methane) the flow rate landfill gas in response detectingthat the measured concentration of the first gas is less than a firstthreshold concentration. Additionally, in such embodiments, one or moreflow control mechanisms may be controlled to decrease (rather thanincrease as the case may be when the first gas is methane) the flow ratelandfill gas in response detecting that the measured concentration ofthe first gas is greater than a first threshold concentration. In suchembodiments, the “YES” branch from decision block 1204 would connect toact 1210 instead of the “YES” branch from decision block 1208, and the“YES” branch from decision block 1208 would connect to act 1206.

As discussed herein, the inventors have developed techniques forcontrolling extraction of landfill gas in order to maximize the energycontent of the extracted gas. In some embodiments, the techniquesinvolve iteratively adjusting the flow rate of extracted landfill gas,based on flow rate and methane concentration measurements, so as tomaximize the product of methane concentration and extracted landfill gasflow rate. The product of methane concentration and gas flow rate mayprovide an estimate of the energy content of landfill gas beingextracted.

FIG. 13 is a flowchart of an illustrative process 1300 for controllingextraction of landfill gas through a gas extraction system with the goalof maximizing the energy content of the landfill gas. Process 1300 maybe performed by any suitable system and, for example, may be performedby control system 500 described herein with reference to FIG. 5. In someembodiments, the entirety of process 1300 may be performed by an in situcontroller and, for example, may be performed by in situ controller 400described herein with reference to FIG. 4. In some embodiments, one ormore acts of process 1300 may be performed by an in situ controller(e.g., in situ controller 400) co-located with a flow-control mechanism(e.g., a valve) and one or more other acts of process 1300 may beperformed by a remote controller (e.g., controller module 504).

Process 1300 begins at act 1302, where a current measure of energycontent in a first portion of extracted landfill gas may be obtained. Insome embodiments, the measure of energy content may be obtained by: (1)measuring the concentration of methane in the first portion of extractedlandfill gas (e.g., using one or more of sensors 205, which may includeat least one sensor configured to sense partial pressure and/orconcentration of methane); (2) measuring the flow rate of extractedlandfill gas (e.g., by using one or more of sensors 205 to determine apressure differential across a venturi, orifice plate, or otherrestriction to the flow of gas; by pitot tube, mechanical flow meter,heated wire or thermal mass flow meter, and/or using any other suitabletechnique); and (3) calculating an estimate of the energy content as aproduct of the measured methane concentration and the determined flowrate. Though, it should be appreciated that the measure of energycontent may be obtained in any other suitable way.

Next process 1300 proceeds to act 1304, where one or more flow controlmechanisms are used to change the flow rate of gas being extracted fromthe landfill. For example, the flow rate of rate of gas may be increasedat act 1304. The flow control mechanism(s) may include one or morevalves, which may be opened to a greater degree in order to increase theflow rate of gas, respectively.

Next process 1300 proceeds to act 1306, where an updated measure ofenergy content in a second portion of extracted landfill gas may beobtained. This measurement may reflect the impact of changes to the gasflow rate made at act 1304 onto the energy content of landfill gas beingextracted. The updated measure of energy content may be obtained in anysuitable way and, for example, may be obtained in the same way asdescribed with reference to act 1302. For example, in some embodiments,the updated measure of energy content may be obtained: (1) measuring theconcentration of methane in the second portion of extracted landfill gas(e.g., using one or more of sensors 205, which may include at least onesensor configured to sense partial pressure and/or concentration ofmethane); (2) measuring the flow rate of extracted landfill gas (e.g.,by using one or more of sensors 205 to determine a pressure differentialacross a venturi, orifice plate, or other restriction to the flow ofgas; by pitot tube, mechanical flow meter, heated wire or thermal massflow meter, and/or using any other suitable technique); and (3)calculating an estimate of the energy content as a product of themeasured methane concentration and the determined flow rate.

Next, process 1300 proceeds to decision block 1308, where it isdetermined whether the updated measure of energy content obtained at act1306 is greater than the current measure of energy content obtained atact 1302. When it is determined that the updated measure of energycontent is greater than the current measure of energy content, process1300 proceeds, via the YES branch, to act 1312 where one or more flowcontrol mechanism(s) are controlled to increase the flow rate of gas.For example, in some embodiments, a single flow control mechanism (e.g.,a valve) may be controlled to increase the flow rate of landfill gas(e.g., by opening the valve to a greater degree). In some embodiments,multiple flow control mechanisms (at a same site or different sites in alandfill) may be controlled to reduce the flow rate of landfill gas. Insome embodiments, a valve may be opened by a predefined increment, forexample, by 5% or by any other suitable amount. In some embodiments, aflow control mechanism may be controlled by an in situ and/or a remotecontroller by receiving one or more control signals from the in situcontroller and/or the remote controller.

On the other hand, when it is determined that the updated measure ofenergy content is not greater than the current measure of energycontent, process 1300 proceeds, via the NO branch, to act 1310 where oneor more flow control mechanism(s) are controlled to decrease the flowrate of gas. For example, in some embodiments, each of one or morevalves may be controlled (e.g., by receiving one or more control signalsfrom one or more controllers) to close to a greater degree (e.g., by apredefined increment of any suitable size or in any other suitable way)in order decrease the flow rate of landfill gas being extracted.

After one of acts 1310 and 1312 is performed, the current measure ofenergy content is changed to be the updated measure of energy content,and process 1300 returns to act 1306, where a new updated measure ofenergy content in another portion of extracted landfill gas is obtained.Thereafter, decision block 1308 and acts 1310, 1312, and 1314 may berepeated. In this way, process 1300 may involve iteratively increasingand/or decreasing the flow rate of gas (e.g., by opening and/or closingone or more valves) in order to extract landfill gas having high energycontent.

It should be appreciated that process 1300 is illustrative and thatthere are variations. For example, in some embodiments, the techniquesfor controlling the extraction of landfill gas may seek to maximizeenergy content in the landfill gas subject to one or more constraints onthe concentration(s) of one or more other gases (e.g., nitrogen and/oroxygen). Limits on concentration of such gases may be imposed bylandfill operators, local regulations, state regulations, and/or federalregulations. Accordingly, in some embodiments, process 1300 may furtherinclude steps to measure concentrations of nitrogen (e.g., by inferringnitrogen concentration as the concentration of balance gas by usingmeasured concentrations of oxygen, methane, and carbon dioxide) and/oroxygen (e.g., using an oxygen sensor).

In turn, at decision block 1308, process 1300 may proceed to act 1312 toincrease the flow rate of landfill gas only when it is determined boththat the updated measure of energy content is greater than the currentmeasure of energy content and the concentration of nitrogen or oxygen isless than a respective threshold (e.g., 2.5% by volume for nitrogen,5.0% by volume for oxygen). Similarly, at decision block 1308, process1300 may proceed to act 1310 to decrease the flow rate of landfill gaswhen it is determined that either the updated measure of energy contentis lower than the current measure of energy content or that the nitrogen(or oxygen) concentration is greater than its respective threshold.

As discussed herein, the inventors have developed techniques forcontrolling extraction of landfill gas that take into account changes inatmospheric conditions, such as atmospheric pressure. In someembodiments, the flow rate of landfill gas being extracted may bedecreased in response to increasing atmospheric pressure and/orincreased in response to decreasing atmospheric pressure. One suchexample embodiment is illustrated in FIG. 14.

FIG. 14 is a flowchart of an illustrative process 1400 for controllingextraction of landfill gas through a gas extraction system based, atleast in part, on atmospheric pressure measurements. Process 1400 may beperformed by any suitable system and, for example, may be performed bycontrol system 500 described herein with reference to FIG. 5. In someembodiments, the entirety of process 1400 may be performed by an in situcontroller and, for example, may be performed by in situ controller 400described herein with reference to FIG. 4. In some embodiments, one ormore acts of process 1400 may be performed by an in situ controller(e.g., in situ controller 400) co-located with a flow-control mechanism(e.g., a valve) and one or more other acts of process 1400 may beperformed by a remote controller (e.g., controller module 504).

Process 1400 begins at act 1402, where a measurement of atmosphericpressure may be obtained. This measured value (the “current atmosphericpressure” value) may be stored for subsequent comparison with one ormore other atmospheric pressure measurements. In some embodiments, themeasurement of atmospheric pressure may be obtained by using one or moreof external sensors 203 (e.g., by an atmospheric pressure sensor) or inany other suitable way.

Next, at act 1404, another measurement of atmospheric pressure (the“updated atmospheric pressure” value) may be obtained. This measurementmay be obtained after a threshold amount of time (e.g., at least 1minute, at least 2 minutes, at least 5 minutes, at least 10 minutes, atleast 30 minutes, at least 1 hour, at least 5 hours, at least 1 day, atleast one week, and/or any suitable threshold in the 1 minute-1 weekrange). The updated atmospheric pressure value may be compared to thecurrent atmospheric pressure value at decision block 1406.

When it is determined that the updated atmospheric pressure value isgreater than the current atmospheric pressure value, process 1400proceeds, via the YES branch, to act 1410 where one or more flow controlmechanism(s) are controlled to increase the flow rate of gas. Forexample, in some embodiments, a single flow control mechanism (e.g., avalve) may be controlled to increase the flow rate of landfill gas(e.g., by opening the valve to a greater degree). In some embodiments,multiple flow control mechanisms (at a same site or different sites in alandfill) may be controlled to reduce the flow rate of landfill gas. Insome embodiments, a valve may be opened by a predefined increment, forexample, by 5% or by any other suitable amount. In some embodiments, aflow control mechanism may be controlled by an in situ and/or a remotecontroller by receiving one or more control signals from the in situcontroller and/or the remote controller.

On the other hand, when it is determined that the updated atmosphericpressure value is not greater than the current atmospheric pressurevalue, process 1400 proceeds, via the NO branch, to act 1408 where oneor more flow control mechanism(s) are controlled to decrease the flowrate of gas. For example, in some embodiments, each of one or morevalves may be controlled (e.g., by receiving one or more control signalsfrom one or more controllers) to close to a greater degree (e.g., by apredefined increment of any suitable size or in any other suitable way)in order decrease the flow rate of landfill gas being extracted.

After one of acts 1408 and 1410 is performed, the current atmosphericpressure value is changed to be the updated atmospheric pressure value,and process 1400 returns to act 1404, where a new updated atmosphericpressure measurement is obtained. Thereafter, decision block 1406 andacts 1408, 1410, and 1412 may be repeated. In this way, process 1400 mayinvolve iteratively increasing and/or decreasing the flow rate of gas(e.g., by opening and/or closing one or more valves) based onatmospheric pressure changes.

It should be appreciated that process 1400 is illustrative and thatthere are variations. For example, in some embodiments, the techniquesfor controlling the extraction of landfill gas based on changes inatmospheric pressure may do so subject to one or more constraints on theconcentration(s) of one or more other gases (e.g., nitrogen and/oroxygen). Limits on concentration of such gases may be imposed bylandfill operators, pipeline operators, local regulations, stateregulations, and/or federal regulations. Accordingly, in someembodiments, process 1400 may further include steps to measureconcentrations of nitrogen (e.g., by inferring nitrogen concentration asthe concentration of balance gas by using measured concentrations ofoxygen, methane, and carbon dioxide) and/or oxygen (e.g., using anoxygen sensor).

In turn, at decision block 1406, process 1400 may proceed to act 1410 toincrease the flow rate of landfill gas only when it is determined boththat there is a decrease in atmospheric pressure and the concentrationof nitrogen or oxygen is less than a respective threshold (e.g., 2.5% byvolume for nitrogen, 5.0% by volume for oxygen). Similarly, at decisionblock 1406, process 1400 may proceed to act 1408 to decrease the flowrate of landfill gas when it is determined that either there is anincrease in atmospheric pressure or that the nitrogen (or oxygen)concentration is greater than its respective threshold.

Site-Level Landfill Gas Extraction Control

Landfill gas collected from multiple different extraction wells in alandfill is aggregated at a gas output. For example, the gas output maybe a power plant that uses the aggregated landfill gas to generateelectricity. In another example, the gas output may be a processingplant where landfill gas collected from the extraction wells undergoestreatment. The inventors have recognized that the power plant mayrequire the aggregated landfill gas to have a certain energy content inorder to process the aggregate landfill gas instead of flaring it.Accordingly, the inventors have developed a control system thatconcurrently controls extraction of landfill gas from multiple wellsbased on a target energy content for the gas output (e.g., power plant,treatment plant). The multiple wells may each have a valve disposed inwell piping coupled to the well that modulates a flow rate of landfillgas being extracted from the well. In some embodiments, the controlsystem may obtain a value indicating a measured energy content oflandfill gas collected at the gas output, and determine whether themeasured energy content is different from a target energy content. Inresponse to determining that the measured energy content is differentfrom the target energy content, the control system may control thevalves disposed in the well piping to control flow rates of landfill gasbeing extracted from the multiple wells. The controller may change thedegree to which each of the valves is open to change the flow rates.

In some embodiments, energy content of landfill gas or other fuel mayindicate an amount of energy per unit of volume or mass of the landfillgas or other fuel. When energy content of landfill gas or other fuelindicates an amount of energy per unit volume of the gas or fuel, theenergy content may be referred to as “energy density”. Some embodimentsof the technology described herein involve controlling gas extractionusing energy content (e.g., based on measured and target energycontent), which encompasses controlling gas extraction using energycontent per unit volume (energy density), energy content per unit ofmass, or any other suitable measure of energy content. In someembodiments, using energy content for controlling gas extraction mayinvolve obtaining a measure of energy content of landfill gas, comparingthe measure of energy content against a target energy content in thelandfill gas, and controlling one or more valves in the landfill gasextraction system based on results of the comparison (e.g., based on thedifference between the measured and target energy content).

The inventors have recognized that landfill gas collected at a gasoutput may be required to meet threshold levels of quality forsubsequent use. For example, a power plant that uses the collectedlandfill gas may require that the landfill gas have energy contentwithin a range of energy content. If the energy content of the collectedlandfill gas is outside of the specified range, the power plant may beunable to use the extracted landfill gas, and the gas may need to beflared. Accordingly, the inventors have developed a control system forperforming error recovery in a situation that the landfill gas collectedat the gas output does not meet a target range of energy content. Insome embodiments, the control system obtains a value indicating ameasured energy content of the landfill gas collected at the gas outputfrom multiple wells. The system determines whether the measured energycontent is within the target range of energy content. In the case thatthe measured energy content is outside of the target range of energycontent, the control system controls multiple valves disposed inwell-piping to change flow rates of landfill gas being extracted fromthe wells. The control system may change the degree to which each of thevalves is open to change the flow rates.

The inventors have recognized that the quality of landfill gas extractedfrom a gas extraction well is affected by a variety of differentfactors. By way of example and not limitation, such factors may includechanges in barometric/ambient pressure, changes in ambient temperature,precipitation, and changes in pressure of a vacuum source. Furthermore,extraction from an individual well may have to be adjusted such thatlandfill gas aggregated from multiple wells meets certain standards(e.g., energy content standards, balance gas limits, etc.). Accordingly,the inventors have developed a system for controlling extraction oflandfill gas from a gas extraction well based on multiple factors. Insome embodiments, the system has a controller that determines one ormore control variables based on measurements of change in pressure of avacuum source, change in barometric pressure outside of the landfill,change in ambient temperature outside of the landfill, and/or a qualityof aggregated landfill gas from multiple wells. The system then controlsa flow control mechanism (e.g., a valve) to adjust a flow rate oflandfill gas being extracted from the gas extraction well based on thecontrol variable(s).

FIG. 15 illustrates an example environment 1500 in which aspects of thetechnology described herein may be implemented. The environment 1500includes a landfill 1502, which holds decomposing waste 1504. Thedecomposing waste 1504 produces landfill gas (LFG) 1506A-C which flowsout from the landfill 1502 through gas extraction wells 1508A-C. A gasextraction well may also be referred to herein as a “well.” The gasextraction wells 1508A-C include respective wellheads 1509A-C. Each ofthe gas extraction wells 1508A-C is coupled to a respective one of thecontrollers 1510A-C through the wellhead of the gas extraction well.Each of the controllers 1510A-C may be configure to locally controlextraction of gas from the gas extraction well that the controller iscoupled to. A controller coupled to a particular well may be referred toherein as a “local controller.” A gas collection system 1512 collectsthe landfill gas extracted from the wells 1508A-C. The gas collectionsystem 1512 supplies the extracted landfill gas to a power plant 1514.The power plant 1514 may be communicatively coupled to a multi-wellcontroller 1516. The multi-well controller 1516 is communicativelycoupled to the controllers 1510A-C associated with wells 1508A-C. Themulti-well controller 1516 receives, from the power plant 1514,information indicating gas quality of landfill gas aggregated from thewells 1508A-C. The multi-well controller 1516 uses the information tofeed control inputs to the local controllers 1510A-C to globally controlextraction of landfill gas at the wells 1508A-C. It should beappreciated that although three wells are shown in FIG. 15, this is byway of example and not limitation, as a site may include any suitablenumber of wells (e.g., at least 10, at least 50, at least 100, at least250, between 50 and 1000 wells).

In some embodiments, the gas collection system 1512 includes a vacuumsource. The vacuum source generates a negative pressure differentialbetween the gas collection system 1512 and the landfill 1502. Thenegative pressure differential causes the landfill gas 1506A-C to flowfrom the landfill 1502 to the gas collection system 1512 through thewells 1508A-C. In some embodiments, the gas collection system 1512 maycomprise an additional location where extracted landfill gas is stored,and/or where the extracted landfill gas may be treated (e.g., byremoving impurities) before being supplied to the power plant 1514. Insome embodiments, the gas collection system 1512 may include aprocessing plant where the collected landfill gas is treated. Thelandfill gas may be treated to modify concentration(s) of one or more ofthe gases that make up the landfill gas. In some embodiments, theprocessing plant may be configured to treat the landfill gas to increasean energy content of the landfill gas. For example, the landfill gas mayinclude methane, oxygen, carbon dioxide, hydrogen sulfide, nitrogen, andother gases. The processing plant may reduce the concentration(s) of oneor more non-methane gases to increase energy content (e.g., energydensity) of the collected landfill gas. The power plant 1514 may beconfigured to generate electricity using the extracted landfill gas. Forexample, the power plant 1514 may burn the extracted landfill gas toturn a rotor of an electricity generator or a turbine. Although the gascollection system 1512 and the power plant 1514 are shown separately inFIG. 15, in some embodiments, the gas collection system 1512 and thepower plant 1514 may be components of a single system.

The power plant 1514 includes one or more sensors 1514A which the powerplant may use to determine one or more measures of quality of extractedlandfill gas. The landfill gas may be collected from multiple wells atthe landfill 1502, such as wells 1508A-C. In some embodiments, thesensor(s) 1514A may be configured to measure an energy content (e.g.,energy density) of collected landfill gas. For example, the sensor(s)1514A may include a gas chromatograph that measures concentrations ofone or more of the gases that make up the collected landfill gas, anduses the concentration(s) to calculate content of energy in thecollected landfill gas. For example, the gas chromatograph may determinea concentration of methane in the collected landfill gas and use it tocalculate the energy content. The multi-well controller 1516 may receiveone or more values indicating the measured quality of collected landfillgas. In some embodiments, the multi-well controller 1516 may receive avalue indicating a measured energy content (e.g., energy density) of thecollected landfill gas.

In some embodiments, each of the local controllers 1510A-C controlsextraction of landfill gas locally at a respective one of the gasextraction wells 1508A-C. The controller may be configured to operate tocontrol extraction of landfill gas to achieve a desired target of energycontent of extracted landfill gas, composition of extracted landfillgas, flow rate of gas extraction, regulatory requirements, and/or otherparameters. In some embodiments, the controller may be configured tocontrol a flow rate of landfill gas being extracted from the well. Forexample, the controller may be configured to control a position of avalve disposed in well-piping of the well which in turn modulates a flowrate of landfill gas being extracted from the well. Example operation ofa controller is described above with reference to FIGS. 1-3. A localcontroller may also be referred to herein as an “in-situ controlmechanism.”

In some embodiments, the multi-well controller 1516 controls extractionof landfill gas globally across multiple gas extraction wells, includingthe gas extraction wells 1508A-C. In some embodiments, the multi-wellcontroller 1516 may be configured to concurrently control extraction oflandfill gas from multiple wells. Concurrently controlling extraction oflandfill gas from multiple wells involves causing an adjustment in avalve at a first well during a first time period, and in a valve at asecond well during a second time period that at least partially overlapswith the first time period. The multi-well controller 1516 may receiveone or more values indicating one or more measures of gas quality oflandfill gas aggregated from multiple wells. In some embodiments, themulti-well controller 1516 may be configured to receive value(s)indicating measured energy content of collected landfill gas. Themulti-well controller 1516 may control the controllers at 1510A-C basedon the measured energy content. In some embodiments, the multi-wellcontroller 1516 may be configured to determine whether the measuredenergy content meets a target energy content and/or is within a targetrange of energy content. In response to determining that the measuredenergy content does not meet the target energy content or is outside thetarget range of energy content, the multi-well controller may adjustflow rates of landfill gas being extracted from the wells 1508A-C. Themulti-well controller 1516 may transmit one or more control inputs tothe controllers 1510A-C to adjust the flow rates.

In some embodiments, each of the controllers 1510A-C may include a valvewhose position controls a flow rate of landfill gas being extracted froma respective well. The multi-well controller 1516 may control thepositions of the valves of the controllers 1510A-C to control, globally,flow rates of landfill gas being extracted from the wells 1508A-C. Insome embodiments, the multi-well controller 1516 may be configured tocontrol the positions of the valves of the controllers 1510A-C bytransmitting a control variable to each of the controllers 1510A-C. Eachof the controllers 1510A-C uses the control variable to determine anadjustment to make to the degree that the valve being controlled by thecontroller is open. In some embodiments, the multi-well controller 1516may transmit a valve position adjustment to each of the controllers1510A-C. The controllers 1510A-C may be configured to apply the receivedadjustment to the respective valves.

In some embodiments, each of the local controllers 1510A-C that controllandfill gas extraction locally may incorporate input from themulti-well controller 1516. For example, a local controller maydetermine one or more adjustments to make to a position of a valve basedon a value of a control variable received from the multi-well controller1516. Additionally or alternatively, in some embodiments, a localcontroller may determine other adjustments to the valve locally based oninput provided from sources other than the multi-well controller 1516.The local controller may be configured to use one or more locallydetermined measures of characteristics of landfill gas being gasextracted from a respective well to determine adjustments. For example,the local controller may determine adjustments based on energy contentand/or concentration of methane in landfill gas being extracted from thewell. In some embodiments, the local controller may be configured tocontrol flow rate of landfill gas being extracted from the well usingmeasures of conditions outside of the well. For example, the localcontroller may use measured or predicted changes in ambient temperature,changes in barometric pressure, and/or changes in vacuum pressure tocontrol the flow rate.

In some embodiments, each of the controllers 1510A-C may be configuredto incorporate input received from the multi-well controller 1516 todetermine control adjustments. For example, the controller may use avalue of a control variable received from the multi-well controller 1516and one or more values of locally determined control variables todetermine an adjustment that is to be applied to a valve of thecontroller. Techniques by which a controller locally controls extractionof landfill gas are discussed herein.

In some embodiments, the multi-well controller 1516 may comprise atleast one computer. The at least one computer may communicate with thecontrollers 1510A-C. In some embodiments, the multi-well controller 1516may be configured to periodically transmit one or more control inputs tothe controllers 1510A-C. In some embodiments, the multi-well controller1516 may wirelessly transmit the control input(s) to the controllers1510A-C. In some embodiments, the multi-well controller 1516 maycommunicate with the controllers 1510A-C over wired connections.

FIG. 16 is a flowchart of an illustrative process 1600 for controllingextraction of landfill gas from multiple gas extraction wells. Process1600 may be performed at least in part by using multi-well controller1516 and multiple local controllers 1510A-C discussed above withreference to FIG. 15.

Process 1600 begins at acts 1602 and 1604 where local adjustments aredetermined by local controllers, and global adjustments are determinedby the multi-well controller.

In some embodiments, each of multiple local controllers determines oneor more adjustments to apply to a flow control mechanism disposed inpiping of a well that the local controller is configured to control. Theflow control mechanism may be a valve disposed in well piping of thewell. The position of the valve may determine a flow rate of landfillgas being extracted from the well. A local controller may be configuredto determine local adjustments based on one or more factors. Thefactor(s) may include characteristics of landfill gas being extractedfrom the landfill, conditions of an environment inside the landfill,conditions of an environment outside of the landfill, a vacuum pressure,and/or other information. In some embodiments, each of the localcontrollers may be configured to (1) obtain measurements of thefactor(s), (2) use the measurements to determine values to determine theadjustment(s) using the measurements.

In some embodiments, the multi-well controller determines one or moreglobal adjustments that are to be applied at multiple wells. Themulti-well controller may be configured to obtain one or more valuesindicating one or more measures of quality of landfill gas collectedfrom the multiple wells, and determine the global adjustment(s) based onthe measure(s) of gas quality. In some embodiments, the multi-wellcontroller may be configured to obtain a value indicating a measuredenergy content of the collected landfill gas. The multi-well controllermay be configured to determine whether the measured energy contentmatches a target energy content. When the multi-well controllerdetermines that the measured energy content does not match the targetenergy content (or is outside a specified range of energy content), themulti-well controller may determine a global adjustment to apply tomultiple valves disposed in well-piping of wells to change flow rates oflandfill gas being extracted from the wells.

Next, process 1600 proceeds to act 1606, where it is determined whetherlandfill gas aggregated from the multiple wells meets targetrequirements. In some embodiments, the requirements may include a rangeof energy content that the aggregated landfill gas must meet in order tobe utilized for an intended function. For example, the aggregatedlandfill gas may be required to have an energy content within aparticular range in order for a power plant to use the landfill gas togenerate electricity. In another example, the aggregated landfill gasmay be required to meet regulatory or government standards of gascomposition.

If at act 1606 it is determined that the aggregated landfill gas doesmeet the requirements, then process 1600 proceeds to act 1610, where thelocal and global control adjustments determined at acts 1602 and 1604are applied to the valves that control flow rates of landfill gasthrough the wells. In some embodiments, the local controllers maycombine the local adjustment(s), and global adjustment(s) to obtain asingle final adjustment that is applied to a respective valve. Forexample, the local adjustments and global adjustments may be combined(e.g., via a sum, a weighted sum, etc.) to obtain a final adjustment toapply to the valve. In some embodiments, the local controller may beconfigured to command movement of an actuator to adjust the degree towhich the valve is open. For example, the controller may modulate athrottle that causes the actuator to change the position of the valve.

If at act 1606 it is determined that the aggregated landfill gas doesnot meet the requirements, then process 1600 proceeds to act 1608 wherethe multi-well controller determines error condition recoveryadjustments to apply globally. In some embodiments, the error conditionadjustments may override or take precedence over local adjustmentsand/or global adjustments determined at acts 1602 and 1604 to insurethat the aggregated landfill gas meets requirements of use. For example,the error condition adjustments may be a default change in position toapply to all the valves to change a quality of landfill gas beingextracted such that the collected landfill gas meets the requirements.

After determining the error condition adjustments, process 1600 proceedsto act 1610 where the error condition adjustments are applied to thevalves. In some embodiments, the local controllers may receive the errorcondition adjustments from the multi-well controller. The localcontrollers may be configured to apply the error condition recoveryadjustments. For example, each local controller commands movement of anactuator to adjust the position of the valves according to the receivederror condition recovery adjustments. In some embodiments, the localcontrollers may be configured to receive a signal indicating an errorrecovery condition. In response, the local controllers may applyreceived signal to control the degree to which a respective valve isopen.

FIG. 17 shows a block diagram of a control system 1700 for locallycontrolling flow of landfill gas at a gas extraction well. In someembodiments, the control system 1700 may be implemented, in part, by oneor more local controllers 1510A-C described above with reference to FIG.15.

In the illustrated embodiment, the system 1700 obtains control variables1702A-E and applies respective gains 1704A-E to the control variables1702A-E to obtain respective adjustments for each of the controlvariables. The control variables 1702A-E may be used as control inputsby the system 1700. The system 1700 includes an accumulator 1706 whichcombines and accumulates the adjustments. The system 1700 includes agate 1708, which prevents application of the adjustments until athreshold adjustment pressure 1710 is reached. The threshold pressure1710 may be a minimum magnitude of adjustment required to triggerapplication of the adjustment by the system 1700. Once the pendingadjustments reach the threshold 1710, the pending adjustments areapplied to a valve actuator 1711 which then causes the position of avalve disposed in piping of a collection well 1712 to change.

In some embodiments, an adjustment to a valve may be specified in termsof a degree to which a valve is to be opened or closed. For example, theadjustment may be a percentage change in position of the valve (e.g.,10% more open or closed). In another example, the adjustment may be anamount by which the valve position is to be changed (e.g., +/−5degrees). In some embodiments, an adjustment may be an absolute positionof the valve. For example, the adjustment may be a percentage specifyinga particular position of the valve (e.g., 0-100% open). In anotherexample, the adjustment may be a degree value specifying an absoluteposition of the valve (e.g., 0-180 degrees).

In the illustrated embodiment, the system 1700 includes a sensor package1714 to obtain measurement(s) of one or more performance metrics. Thesystem 1700 includes a latch 1716 for storing a previous measurement ofthe performance metric(s). The system 1700 compares a measurement of theperformance metric(s) taken after application of an adjustment to ameasurement of the performance metric(s) taken prior to the applicationof the adjustment. The result of the comparison is used as feedbackcontrol input 1702E. In some embodiments, a performance metric may be anenergy content of landfill gas being extracted from the collection well1712, a concentration of methane in the landfill gas being extractedfrom the collection well 1712, and/or a flow rate of landfill gas beingextracted from the collection well 1712.

In the illustrated embodiment, the system 1700 includes a secondaccumulator 1709 which accumulates adjustments that have been applied tothe valve actuator 1711. The applied adjustments that have beenaccumulated by the accumulator 1709 are subtracted from pendingadjustments such that the adjustments may be applied in discreteincrements. For example, if a pending adjustment of 5 degrees meets theaction threshold 1710, and is applied to the valve actuator 1711, the 5degree adjustment that is applied to the valve actuator 1711 is trackedby the accumulator 1709. In a subsequent control cycle, the pendingadjustment value may remain at 5 degrees. The previous 5 degreeadjustment tracked by the accumulator 1709 is subtracted from thepending adjustment value such that the adjustment pressure is 0.Accordingly, no additional adjustment is applied to the valve actuator1711. This allows pending adjustments to be applied in discreteincrements such that an effect of an applied adjustment can be measuredby the sensor package 1714.

In some embodiments, the system 1700 may be configured to use a measuredchange in vacuum pressure 1702A as a control input. The change in vacuumpressure 1702A may indicate a change in a pressure differential betweena gas output and the landfill. The pressure differential causes landfillgas to flow from the landfill to the gas output through collection well1712. The system 1700 may apply a tunable gain parameter (−K_(V)) 1704Ato the measured change in vacuum pressure. If the pressure differentialdecreases by a certain amount, the system may obtain an adjustment toreduce a flow rate of landfill gas being extracted from the collectionwell 1712. For example, the adjustment may be one that results inclosing the valve further. If the pressure differential increases by acertain amount, the system may obtain an adjustment to increase a flowrate of landfill gas being extracted from the collection well 1712. Forexample, the adjustment may be opening the valve further.

In some embodiments, the system 1700 may be configured to use a measuredchange in barometric pressure 1702B as a control input. The change inbarometric pressure may be measured over a period of time. An increasein barometric pressure over the period of time may increase a pressuredifferential between the landfill and air outside of the landfill. As aresult, more air may permeate into the landfill and affect compositionof landfill gas being extracted from the landfill. In some instances,this may result in decreased concentration of methane in the land fillgas which results in the landfill gas having a lower energy content. Thesystem may apply a gain parameter (−K_(B)) 1704B to the measured changein barometric pressure. If there is a positive change in barometricpressure, the system may determine a corresponding adjustment to reducea flow rate of landfill gas being extracted from the well 1712 tomitigate effects of the rise in pressure. If there is a negative changein barometric pressure, the system may determine a correspondingadjustment to increase a flow rate of landfill gas being extracted fromthe well 1712.

In some embodiments, the system 1700 may be configured to continuouslyobtain measurements of the barometric pressure. In some embodiments, thesystem 1700 may be configured to obtain a measurement every 1 minute, 2minutes, 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes, 8minutes, 9 minutes, or 10 minutes. In some embodiments, the system 1700may be configured to calculate a running average rate of change ofbarometric pressure. In some embodiments, the system 1700 may beconfigured to determine whether the magnitude of the calculated rate ofchange of the barometric pressure is greater than a threshold rate ofchange. In response to determining that the magnitude of the calculatedrate of change is greater than the threshold rate of change, the system1700 may trigger a response to the change in barometric pressure. Ifthere is a positive change in the rate of change of the barometricpressure, the system may determine a corresponding adjustment to reducea flow rate of landfill gas being extracted from the well 1712 tomitigate effects of the rise in pressure. If there is a negative changein the rate of change of the barometric pressure, the system maydetermine a corresponding adjustment to increase a flow rate of landfillgas being extracted from the well 1712.

In some embodiments, the threshold rate of change may be 0.05 mbar/hour,0.1 mbar/hour, 0.15 mbar/hour, 0.2 mbar/hour, 0.25 mbar/hour, 0.3mbar/hour, 0.35 mbar/hour, 0.4 mbar/hour, 0.5 mbar/hour 0.55 mbar/hour,0.6 mbar/hour, 0.65 mbar/hour, 0.7 mbar/hour, 0.75 mbar/hour, 0.8mbar/hour, 0.85 mbar/hour, 0.9 mbar/hour, 0.95 mbar/hour, or 1mbar/hour.

In some embodiments, the system 1700 may be configured to use a measuredchange in ambient temperature 1702C as a control input. When an ambienttemperature outside of the landfill decreases by a certain amount, thepermeability of a covering placed over the landfill may increase. As aresult, additional air from the atmosphere around the landfill may enterthe landfill and affect composition of the landfill gas being extracted.For example, a concentration of methane in the landfill gas beingextracted may be reduced, which results in reduced energy content of thelandfill gas being extracted. The system 1700 may be configured to applya gain parameter (K_(T)) 1704C to the measured change in ambienttemperature. If the ambient temperature decreases over a period of time,the system may obtain a corresponding adjustment that reduces a flowrate of landfill gas from the well 1712 to mitigate effects of the dropin temperature. If the ambient temperature increases, the system mayobtain a corresponding adjustment to increase a flow rate of landfillgas being extracted from the well 1712.

In some embodiments, the system 1700 may be configured to use anaggregate gas quality control variable 1702D. The aggregate gas qualitycontrol variable may be obtained from a multi-well controller thatdetermines global adjustments to be applied to multiple gas extractionwells at a landfill. The aggregate gas quality control variable may bedetermined as described below with reference to FIG. 18. The system 1700may apply a gain parameter (K_(S)) 1704D to the aggregate gas qualitycontrol variable 1702D. The system may determine an adjustment toincrease the flow rate of landfill gas being extracted from the well1712 in response to more positive values of the control variable, and anadjustment to decrease the flow rate of landfill gas being extractedfrom the well 1712 in response to more negative values of the controlvariable.

In some embodiments, the system 1700 may be configured to use a feedbackcontrol input 1702E determined based on a measured effect of one or moreapplied adjustments. In some embodiments, the system may be configuredto implement a greedy hill climbing feedback input. The system 1700 maymultiply a measured effect of the performance metric(s) of an appliedadjustment by the applied adjustment. If the applied adjustment resultedin a negative effect on the performance, the feedback 1704E will be anopposite of the applied adjustment. For example, if an appliedadjustment of +1 degrees resulted in a −2% decrease in concentration ofmethane, the value of the feedback input 1702E will be −2 which is inthe opposite direction of the applied adjustment. Conversely, if theapplied adjustment resulted in a positive effect on the performance, thefeedback 1704E will continue in a direction of the applied adjustment.For example, if an applied adjustment of +1 degrees results in a +2%increase in concentration of methane, the value of the feedback input1702E will be 2. The system 1700 may apply a gain parameter (K_(G))1704E to the feedback 1702E.

In some embodiments, the system 1700 may be configured to use apredicted change in barometric pressure as a control input. An increasein barometric pressure may affect landfill gas being extracted from thewell 1712. Using predicted changes in barometric pressure may allow thesystem 1700 to bias a flow of landfill gas to mitigate effects of futureactual changes in barometric pressure on landfill gas being extractedfrom the well 1712. The system 1700 may apply a gain parameter to apredicted change in barometric pressure. If the system obtains apredicted increase in barometric pressure, the system may obtain acorresponding adjustment to decrease a flow rate of landfill gas beingextracted from the well 1712. If the system obtains a predicted decreasein barometric pressure, the system may obtain a corresponding adjustmentto increase a flow rate of landfill gas being extracted from the well1712.

In some embodiments, the system 1700 may be configured to use apredicted change in ambient temperature as a control input. As describedabove, a change in ambient temperature may affect landfill gas beingextracted from the well 1712. Using predicted changes in ambienttemperature may allow the system 1700 to bias the flow of landfill gasto mitigate effects of future changes in the ambient temperature on thelandfill gas being extracted from the well 1712. The system 1700 mayapply a gain parameter to a predicted change in ambient temperature. Ifthe system obtains a predicted increase in ambient temperature pressure,the system may obtain a corresponding adjustment to increase a flow rateof landfill gas being extracted from the well 1712. If the systemobtains a predicted decrease in ambient temperature, the system mayobtain a corresponding adjustment to decrease a flow rate of landfillgas being extracted from the well 1712.

In some embodiments, the system 1700 may use other control inputs inaddition to or instead of those illustrated in FIG. 17. In someembodiments, the system 1700 may be configured to use a value indicatinga measured current precipitation and/or predicted precipitation outsideof the landfill as a control input. A change in precipitation may affectlandfill gas being extracted from the landfill. For example, the valuemay indicate a measured amount of precipitation (e.g., inches) and/or atype of precipitation (e.g., snow, rain, hail). Some embodiments are notlimited to any particular set of control inputs. Some embodiments mayuse any combination of control inputs discussed herein.

In some embodiments, the system 1700 may be configured to obtain valuesof one or more control inputs using local sensors. For example, valuesof control inputs 1702A-C may be obtained using sensors that are part ofthe control system. In some embodiments, the system 1700 may beconfigured to receive values of one or more control inputs from anexternal system. For example, the system 1700 may access barometricpressure changes, ambient temperature changes, forecasted barometricpressure changes, and forecasted ambient temperature changes from acomputer separate from the system 1700.

In some embodiments, the gain parameters used by the system may betunable. Different wells may react differently to various changes. Thegain parameters may be tuned based on unique characteristics of the well1712. For example, methane concentration in landfill gas being extractedfrom a first well may be more sensitive to changes in flow rate thanlandfill gas being extracted from a second well. Each well may have aset of gain parameters that have been tuned for the well. In someembodiments, gain parameters at each well may be tuned to maximizeperformance at the well. In some embodiments, gain parameters may betuned such that effects of control inputs are uniform across differentwells. In some embodiments, the gain parameters may be tuned manually orautomatically.

In some embodiments, the system 1700 may utilize different gains forcontrolling the opening and closing of the valve. For example, a firstset of one or more gains may be used for controlling opening of thevalve and a second set of one or more gains may be used for controllingclosing of the valve, with the first and second sets of gains beingdifferent from one another. For example, different vacuum pressurechange gains K_(V) may be used for controlling opening and closing avalve. Additionally or alternatively, different barometric pressurechange gains K_(B) may be used for controlling opening and closing avalve. Additionally or alternatively, different ambient temperaturechange gains K_(T) may be used for controlling opening and closing avalve. Additionally or alternatively, different ambient temperaturechange gains K_(T) may be used for controlling opening and closing avalve. Additionally or alternatively, different aggregate gas qualitycontrol gains K_(S) may be used for controlling opening and closing avalve. Additionally or alternatively, different feedback gains K_(G) maybe used for controlling opening and closing a valve. Additionally oralternatively, different action thresholds 1710 may be used forcontrolling opening and closing a valve. Thus, it should be appreciatedthat different gains for any one or more of the gains K_(V), K_(B),K_(S), K_(T), K_(G) and action thresholds may be used for controllingopening and closing of the valves.

In some embodiments, one or more of the gains for a valve may be basedon how quickly the composition of gas flowing through a valve from awell changes as a result of a valve adjustment. When the composition ofgas changes more rapidly in response to a valve adjustment operation(e.g., closing or opening), then the gain for that valve operation maybe set to a lower value. When the composition of gas changes more slowlyin response to a valve adjustment operation, then the gain for thatvalve operation may set to a higher value. For example, suppose that thecomposition of gas flowing through a valve from a well changes morerapidly in response to opening of a valve than to closing of the valve.In that situation, one or more gains of the valve may be set lower(e.g., a first gain) for the opening adjustment than for the closingadjustment (e.g., a second gain larger than the first gain).

In some embodiments, the system 1700 may include a gate 1708 that allowsapplication of adjustments that meet a threshold 1710 level ofadjustment. In some embodiments, the threshold 1710 may be tuned toadjust sensitivity of the system 1700 to adjustments. For example, alower threshold 1710 will allow adjustments to be applied morefrequently, and will allow application of finer adjustments. A higherthreshold 1710 will limit frequency of adjustments applied, and willlimit application to coarser adjustments. In some embodiments, thethreshold 1710 may be tuned to balance stability of the system 1700 withprecision of control. In some embodiments, the controller may havelimited power resources, and the gate 1708 may moderate a frequency ofapplication of adjustments to limit use of the power. For example, acontroller may be powered by a solar panel which stores energy. The gate1708 may limit application of adjustments to conserve the stored energy.

In some embodiments, the threshold 1710 may be a minimum percentage ofchange. For example, the threshold may be a magnitude of 1%, 2%, 3%, 5%,10%, 15%, or 20%. In some embodiments, the threshold may be a particularnumber of degrees. For example, the threshold may be 1 degree, 2, 3, 5,10, 15, 20, or 25 degrees.

In some embodiments, the system 1700 may be configured to maintain oneor more limits of the position of the valve. The limit(s) may bereferred to as “guard rails.” The system 1700 may be configured toprevent adjustments to the position of the valve beyond the limit(s). Insome embodiments, the system 1700 may prevent the valve from openingbeyond a first limit and/or closing beyond a second limit. The limit maybe a particular position of the valve. For example, the system 1700 mayprevent the valve from opening beyond a position of 80 degrees. Inanother example, the system 100 may prevent the valve from closing morethan a position of 5 degrees. In yet another example, the system 1700may prevent the valve from opening beyond a position of 90% open. In yetanother example, the system 1700 may not allow the valve to close beyonda position of 10% open.

In some embodiments, the system 1700 may be configured to maintain athreshold concentration of one or more of the gases that make up thelandfill gas. In some embodiments, the system 1700 may be configured todetermine if a measured concentration of oxygen in the landfill gas isabove a maximum oxygen concentration. If the system 1700 determines thatthe measured concentration of oxygen is above the maximum oxygenconcentration, the system 1700 may restrict a flow of landfill gas. Forexample, the system 1700 may prevent adjustments that further open thevalve. In another example, the system 1700 may close the valve by acertain amount. In some embodiments, the system 1700 may be configuredto determine if a measured concentration of nitrogen in the landfill gasis above a maximum nitrogen concentration. If the system 1700 determinesthat the measured concentration of nitrogen is above the maximumnitrogen concentration, the system 1700 may restrict a flow of landfillgas. For example, the system 1700 may prevent adjustments that furtheropen the valve. In another example, the system 1700 may close the valveby a certain amount. In some embodiments, the system 1700 may beconfigured to determine if a measured concentration of methane in thelandfill gas is above a maximum methane concentration. If the system1700 determines that the measured concentration of methane is above themaximum methane concentration, the system 1700 may restrict a flow oflandfill gas. For example, the system 1700 may prevent adjustments thatfurther open the valve. In another example, the system 1700 may closethe valve by a certain amount.

FIG. 18 shows a block diagram of a control system 1800 for globallycontrolling flow of landfill gas at multiple gas extraction wells. Insome embodiments, the control system 1800 may be implemented by amulti-well controller 1516 described above with reference to FIG. 15.

In some embodiments, the system 1800 may be configured to determine aglobal adjustment to apply to valves at multiple gas extraction wells ofa landfill. The system 1800 may obtain a target energy content 1802 ofaggregated landfill gas being extracted from the multiple wells. In someembodiments, the target energy content 1802 may be in units of Britishthermal units per standard cubic foot (BTU/SCF). The system maydetermine an error between the target energy content 1802 and a measuredenergy content 1804 of aggregated landfill gas extracted from the wells.The system 1800 may obtain a value indicating the measured energycontent 1804 from a gas chromatograph 1814. The system 1800 maydetermine an error between the target energy content 1802 and themeasured energy content 1804. The error value is input into aproportional integral derivative (PID) controller 1808 to generate aglobal adjustment value. The value of the global adjustment may betransmitted to multiple local controllers 1810A-C coupled to respectivewells. Each of the local controllers 1810A-C may use the globaladjustment as a control variable in determining an adjustment to applyto a respective valve. For example, the global adjustment may bereceived as aggregate gas control variable 1702D by a local controlsystem 1700 as described above with reference to FIG. 17. The localcontroller may apply a gain to the aggregate control variable to obtaina corresponding adjustment. In some embodiments, the local controllermay not apply a gain value to the global adjustment and use a valuedirectly as received from the multi-well controller.

In some embodiments, the system 1800 may be configured to transmit thedetermined global adjustment to the local controllers 1810A-C. In someembodiments, the system may be configured to transmit the globaladjustment periodically. For example, the system may transmit the globaladjustment every second, minute, every 15 minutes, every 30 minutes, orevery hour. In some embodiments, the system 1800 may be configured totransmit the global adjustment to each of the local controllers 1810A-Cin response to a request from the local controllers. For example, thesystem 1800 may receive a signal pinging the system 1800 for a value ofthe global adjustment. In response, the system 1800 may transmit thevalue of the global adjustment to a controller from which the signal wasreceived.

In the illustrated embodiment, the landfill gas extracted from themultiple wells is collected at a gas processing plant 1812. In someembodiments, the gas processing plant may purify and/or filter theaggregated landfill gas. In some embodiments, the gas processing plantmay be part of a power plant that uses the aggregated gas to generateelectricity. The system 1800 then obtains a value indicating a measuredenergy content of the aggregated gas from a gas chromatograph 1814 basedon which the system 1800 can calculate an error for a subsequent controlcycle.

In some embodiments, the system 1800 may include a filter 1806 toinhibit error values that would result in reduction of energy content.For example, the filter may be a function max(0, Error) that filters outnegative error values. The system 1800 may determine global adjustmentsto maintain a measured energy content 1804 that is above the targetenergy content 1802. In some embodiments, the system 1800 does notinclude the filter 1806. The system 1800 may input positive or negativeerror values into the PID controller 1808 for generating a globaladjustment. The system 1800 may then determine global adjustments tosuch that the measured energy content 1804 tracks the target energycontent 1802.

In some embodiments, the system 1800 may use a different type ofcontroller in addition to or instead of a PID controller. For example,the system 1800 may use a proportional integral (PI controller). Inanother example the system 1800 may use proportional derivative (PD)controller. In yet another example, the system 1800 may apply aproportional gain to the error.

In some embodiments, the target energy content (e.g., target energydensity) may be 930 BTU/SCF, 935 BTU/SCF, 940 BTU/SCF, 945 BTU/SCF, 950BTU/SCF, 955 BTU/SCF, 955 BTU/SCF, 960 BTU/SCF, 965 BTU/SCF, 970BTU/SCF, 975 BTU/SCF, 980 BTU/SCF, 985 BTU/SCF, or 990 BTU/SCF.

In some embodiments, the system 1800 may be configured to obtain thetarget energy content from a separate computer. For example, the system1800 may receive the target energy content from a computer at a powerplant. In some embodiments, the target energy content may be stored orprogrammed into a multi-well controller implementing the system 1800.

In some embodiments, the system 1800 may be configured to use adifferent target metric of gas quality in addition to or instead ofenergy content. In some embodiments, the system 1800 may be configuredto obtain a target methane concentration of landfill gas being extractedfrom the wells. The system 1800 may obtain a value indicating a measuredconcentration of methane in landfill gas extracted from the wells. Thesystem 1800 may then determine the error between the target methaneconcentration and the measured methane concentration.

FIG. 19 is a flowchart of a process 1900 for performing error conditionrecovery in a landfill gas extraction system. In some embodiments,process 1900 may be performed by multi-well controller 1516 discussedabove with reference to FIG. 15.

Process 1900 begins at act 1902 where the system performing process 1900determines whether energy content of landfill gas collected frommultiple gas extraction wells is greater than a first threshold energycontent. In some embodiments, the system may be configured to obtain avalue indicating a measured energy content of the collected landfillgas. For example, the system may receive the value from one or moresensors of a power plant that received the collected landfill gas. Insome embodiments, the system may include one or more sensors thatmeasure the energy content.

In some embodiments, the first threshold energy content may be a maximumenergy content required at a gas output. For example, a power plant mayrequire that collected landfill gas have at most the first thresholdenergy content for the landfill gas to be used for generatingelectricity. In some embodiments the first threshold energy content is910, 920, 930, 940, 950, 960, 970, 980, 990, or 1000 BTU/SCF.

If at act 1902 the system determines that the measured energy content isgreater than the first threshold energy content, then process 1900proceeds to act 1904, where the system obtains a first error recoveryadjustment to apply to multiple valves disposed at multiple wells in alandfill. In some embodiments, the first error recovery adjustment maybe an adjustment to open the valves to increase flow of landfill gasbeing extracted from the wells.

In some embodiments, the first error adjustment is opening the valves by0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 degrees. Insome embodiments, the first error adjustment is opening the valves by20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170,or 180 degrees. In some embodiments, the first error adjustment isopening the valves to a maximum open position. In some embodiments, thefirst error adjustment is opening the valves by 1%, 5%, 10%, 15%, 20%,25%, 30%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or100%. In some embodiments, the first error recovery adjustment may bestored in a memory of the system. In some embodiments, the first errorrecovery adjustment may be received by the system from a computerseparate from the system.

Next, process 1900 proceeds to act 1906 where the system determines asubset of wells at which to apply the first error recovery adjustmentobtained at act 1904. In some embodiments, the system may be configuredto determine all the wells at which landfill gas being extracted has (1)a measured concentration of methane that is greater than a firstthreshold concentration of methane, and (2) a temperature less than orequal to a temperature threshold. In some embodiments, the firstthreshold concentration of methane is 50%, 55%, 56%, 57%, 58%, 59%, 60%,61%, 62%, 63%, 64%, or 65%. In some embodiments, the temperaturethreshold is 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150degrees Celsius. In some embodiments, local controllers coupled to thewells may be configured to determine whether landfill gas beingextracted from respective wells meet the criteria. For example, each ofthe local controllers may receive a signal from the multi-wellcontroller indicating of an error condition in which the aggregateenergy content is greater than the first threshold energy content. Inresponse, each local controller may determine whether the landfill gasbeing extracted from a respective well that the local controller iscoupled to meets the two criteria. The local controller may use one ormore sensors to obtain a measurement of the concentration of methane inthe landfill gas being extracted and a measurement of temperature of thelandfill being extracted. The local controller may use the measurementsto determine whether landfill gas being extracted from a respective wellmeets the criteria.

Next, process 1900 proceeds to act 1908, where the system applies thefirst error recovery adjustment obtained at act 1904 to the identifiedsubset of wells. In some embodiments, each of the of local controllersmay be configured to apply the first error recovery adjustment inresponse to determining that landfill gas being extracted from arespective well has a measured methane concentration greater than thefirst threshold concentration of methane and a measured temperature lessthan or equal to the temperature threshold. In some embodiments, thelocal controller may override other adjustments determined by thecontroller. For example, the local controller may override adjustmentsdetermined from control inputs, or other global adjustments. The localcontroller may control an actuator to apply the first error recoveryadjustment. In some embodiments, the local controller may be configuredto apply a gain factor to the error recovery adjustment value receivedfrom the multi-well controller. The gain factor may modify the receivederror recovery adjustment for the well. The gain factor may be tuned foreach of the wells. If at act 1902 the system determines that themeasured energy content of the collected landfill gas is less than thefirst threshold energy content, then process 1900 proceeds to act 1910where the system determines whether the measured energy content is lessthan a second threshold energy content. In some embodiments, the secondthreshold energy content may be a minimum energy content required at agas output. For example, a power plant may require that collectedlandfill gas have at least the second threshold energy content for thelandfill gas to be used for generating electricity. In some embodimentsthe second threshold energy content is 900, 910, 920, 930, 940, 950,960, 970, 980, or 990 BTU/SCF.

If at block 1910 the system determines that the measured energy contentis greater than the second threshold energy content, then process 1900proceeds to act 1902 where the system again determines whether ameasured energy content of landfill gas collected from multiple wells isgreater than the first threshold energy content. In some embodiments,the system may obtain an updated value indicating the measured energycontent of the collected landfill gas.

If at act 1910 the system determines that the measured energy content isless than the second threshold energy content, then process 1900proceeds to block 1912 where the system obtains a second error recoveryadjustment to apply to multiple valves disposed at multiple wells in alandfill. In some embodiments, the second error recovery adjustment maybe an adjustment to close the valves to restrict flow of landfill gasbeing extracted from the wells.

In some embodiments, the second error recovery adjustment is closing thevalves by 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15degrees. In some embodiments, the first error adjustment is closing thevalves by 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150,160, 170, or 180 degrees. In some embodiments, the first erroradjustment is closing the valves to a maximum closed position. In someembodiments, the first error adjustment is closing the valves by 1%, 5%,10%, 15%, 20%, 25%, 30%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%,85%, 90%, 95%, or 100%. In some embodiments, the second error recoveryadjustment may be stored in a memory of the system. In some embodiments,the second error recovery adjustment may be received by the system froma computer separate from the system.

Next, process 1900 proceeds to block 1914 where the system identifies asubset of wells at which landfill gas being extracted has a measuredconcentration of methane that is less than a second thresholdconcentration of methane. In some embodiments, the second thresholdconcentration of methane is 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%,39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%,53%, 54%, 55%, 56%, 57%, 58%, 59%, or 60%. In some embodiments, localcontrollers coupled to the wells may be configured to determine whetherlandfill gas being extracted from respective wells meet the criteria.For example, multiple local controllers may receive a signal from themulti-well controller indicating of an error condition in which theaggregate energy content is less than the second threshold energycontent. In response, each local controller may determine whether thelandfill gas being extracted from a respective well that the localcontroller is coupled to has a measured concentration of methane lessthan the second threshold concentration of methane. The local controllermay use one or more sensors to obtain a measurement of the concentrationof methane in the landfill gas being extracted.

Next, process 1900 proceeds to act 1908 where the system applies thesecond error recover adjustment obtained at act 1912 to the subset ofwells identified at act 1914. In some embodiments, each of the of localcontrollers may be configured to apply the second error recoveryadjustment in response to determining that landfill gas being extractedfrom a respective well has a measured methane concentration less thanthe second threshold concentration of methane. In some embodiments, thelocal controller may be configured to override other adjustmentsdetermined by the controller. For example, the local controller mayoverride adjustments determined from control inputs, or other globaladjustments. The local controller may control an actuator to apply thesecond error recovery adjustment. In some embodiments, the localcontroller may be configured to apply a gain factor to the errorrecovery adjustment value received from the multi-well controller. Thegain factor may modify the received error recovery adjustment for thewell. The gain factor may be tuned for each of the wells.

After applying obtained error recovery adjustments at act 1908, process1900 proceeds to act 1902 where the system again determines whether ameasured energy content of landfill gas collected from multiple wells isless than a first threshold energy content. In some embodiments, thesystem may obtain an updated value indicating the measured energycontent of the collected landfill gas. In some embodiments, the systemmay be configured to wait a period of time after applying the determinederror recovery adjustment at act 1908. In some embodiments, the periodof time may be 15 minutes, 30 minutes, 45 minutes, 1 hour, 1.5 hours, 2hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10hours, 12 hours, or 1 day.

Proportional Response

Some of the automated control techniques described herein involveadjusting the degree to which one or more valves are open or closedbased on the difference between a measured value of a quantity (e.g.,BTU, energy content in gas, percentage of a particular type of gas suchas methane or oxygen or nitrogen in the landfill gas, etc.) and a targetvalue for that quantity. In some embodiments, when it is determined thata valve is to be closed or opened, the valve is controlled to close oropen by a fixed amount. In some embodiments, when it is determined thata valve is to be closed or opened, the valve is controlled to close oropen by an amount that depends on the difference between the measuredvalue of the quantity and the target value for that quantity. Forexample, when closing the valve serves to decrease the differencebetween the measured value and the target value of a quantity, then thevalve may be closed to a greater degree when the difference between themeasured and target values is large than when that difference is small.In this way, a valve may be closed and opened by an amount proportionalto the difference between the measured and target value of the quantityused for control. As a further example, in some embodiments, when themeasured gas composition at the plant is farther away from the desiredgas composition, the batch valve open/close command may be greater (asreflected by the larger gains utilized).

Automated Shutoff

In some embodiments, automated control of one or multiple valves in alandfill gas extraction system may be stopped in response to receivingone or more unexpected measurements from one or more sensors parts ofthe automated control system. In this way, valve adjustments determinedby any of the automated control techniques described herein are notdetermined based on erroneous sensor readings, especially erroneoussensor readings at the power plant.

For example, in some embodiments, automated control may be stopped inresponse to obtaining gas composition measurement (e.g., from powerplant equipment) outside of one or more specified ranges for constituentgasses. As another example, in some embodiments, automated control maybe stopped in response to obtaining a BTU measurement (e.g., from powerplant equipment) outside of a specified BTU range. For example,automated control may be stopped in response to obtaining a BTUmeasurement outside of the range of 940-1000 BTUs.

After automated control is stopped, it may be restarted in any suitableway. For example, in some embodiments, the automated control may berestarted after a threshold amount of time has elapsed. As anotherexample, in some embodiments, the automated control may be restarted inresponse to updated measurements falling within the specified ranges.For instance, if automation control was stopped in response to ameasurement of a quantity falling outside of a specified range of“normal” values for that quantity, automated control may be restartedwhen a subsequent measurement of that same quantity is within thespecified range. As yet another example, in some embodiments, automatedcontrol may be resumed in response to user input (e.g., provided througha computer interface, such as a graphical computer interface) indicatingthat the automated control is to be resumed.

Current and Predicted Measurements

The automated control techniques described herein, in some embodiments,control the degree to which one or more valves are open based on one ormore sensor measurements (e.g., one or more measurements of gascomposition, flow rate, ambient temperature, barometric pressure, BTUmeasurements at the power plant, etc.). The inventors have recognizedthat, while such valve adjustments can be effective, in some embodimentsthe impact of the adjustments takes time to take effect. In other words,the overall response time in the system to a valve adjustment may beslower than desired.

The inventors have recognized that, in some circumstances, the responsetime to valve adjustments may be reduced, by using a predicted value ofa quantity to control the valves instead of a currently measured valueof that same quantity. By way of example, suppose that valve control isbeing performed, in part, based on the percentage of methane in landfillgas. The first measurement may indicate that the percentage of methaneis 46%. An hour later, the second measurement may indicate that thepercentage of methane is 45%. Another hour later, the third measurementmay indicate that the percentage of methane is 44%. A valve adjustmentcould be made, each hour, based on these measurements. However, by usingthe 46% and 45% measurements, it may be possible to predict that, in anhour, the predicted value of methane concentration would be 44%. If sucha prediction could be made, then the automated control techniques coulddetermine the degree(s) to which to close/open one or more respectivevalues based on the predicted value (i.e., 44%) rather than the measuredvalues of 46% and 45%, and to do so before the 44% value would bemeasured (an hour later) thereby reducing the overall time needed tocontrol the gas extraction system to a target state.

Accordingly, in some embodiments, one or more (e.g., two, three, etc.)measured values of a quantity (e.g., one or more measurements of gascomposition, flow rate, ambient temperature, barometric pressure, BTUmeasurements at the power plant, etc.) may be used to predict a valuethat quantity is likely to take during a specified time period in thefuture (e.g., 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60 minutes,2 hours, 3 hours, between 1 and 5 minutes, between 10 and 20 minutes,between 30 minutes and 2 hours, or any range within these ranges). Insome embodiments, two measurements may be used to obtain a predictedvalue using linear projection (e.g., measure the slope of the linedefined by the two measurements and use the measured slope to predict athird value). In embodiments, where a larger number of measurements isused (i.e., three or more), a higher order polynomial projection may beperformed.

It should be appreciated that any of the control techniques describedherein may use predicted values of measurements for any of thequantities utilized for control (e.g., gas composition, flow rate,ambient temperature, barometric pressure, BTU measurements at the powerplant, etc.). In some embodiments, predicted values may be used for allthe quantities utilized for control. In some embodiments, one or morepredicted values and one or more measured values may be utilized forcontrol. In some embodiments, prediction may not be employed, and onlymeasured values may be used.

Pressure Control

A landfill gas extraction system extracts landfill gas from a collectionwell by using a vacuum source to create a negative pressure differentialbetween the landfill and a gas output (e.g., a gas treatment plant,and/or a power plant). The negative pressure differential causeslandfill gas to flow from the landfill to the gas output through wellpiping of the gas extraction system. A positive pressure in well pipingof the gas extraction system may cause landfill gas to be released intothe atmosphere. Landfill gas may have an unpleasant odor. Additionally,landfill gas may contain methane and CO2 which are greenhouse gases thatcontribute to atmospheric warming. For these reasons, operators of gasextraction systems may be required to take corrective action if it isdetermined that landfill gas is being released into the atmosphere.

In conventional gas extraction systems, operators review measurements oflandfill gas pressure in the well piping of a gas extraction system todetermine if there is a risk of landfill gas being released into theatmosphere. These measurements are collected manually (e.g., everymonth). Operation compliance requirements may require an operator tomake a corrective manual adjustment at the gas extraction system if ameasurement indicates that there is a risk of landfill gas beingreleased from the gas extraction system into the atmosphere. Forexample, the operator may be required to make an adjustment to amanually controlled valve.

The inventors have recognized that a gas extraction system mayfrequently enter a state in which landfill gas is being released intothe atmosphere between collected measurements. For example, changes inenvironmental conditions such as barometric pressure may result in apositive landfill gas pressure in the well piping of the gas extractionsystem that causes landfill gas to be released into the atmosphere. Asanother example, control adjustments (e.g., valve position adjustments)made to the gas extraction system may result in a positive landfill gaspressure in the well piping that causes landfill gas to be released intothe atmosphere. Conventional gas extraction systems fail to detectinstances between collected measurements during which there is a risk oflandfill gas being released into the atmosphere due to a positivepressure inside the gas extraction system. As a result, the gasextraction system may be releasing landfill gas into the atmosphere, andviolating compliance requirements without detection or corrective actionbeing performed.

Accordingly, the inventors have developed a control system thatautomatically: (1) determines whether a gas extraction system is in astate in which there is a risk of landfill gas being released into theatmosphere; and (2) automatically controls landfill gas flow to mitigatethe risk and/or stop a release of landfill gas. In some embodiments, thecontrol system may be configured to control a valve to control flow oflandfill gas through well piping of the gas extraction system. If thelandfill gas pressure at a location upstream of the valve is positive,this may indicate that the gas extraction system is in a state in whichthere is a risk of landfill gas being released into the atmosphere. Insome embodiments, the control system may include a pressure sensor tomeasure the landfill gas pressure at the location upstream of the valve.The control system may be configured to automatically control the valveto reduce the landfill gas pressure at the location upstream of thevalve if the sensor indicates that the landfill gas pressure at thelocation upstream of the valve is above a threshold pressure (e.g., −0.1mbar). The control system may prevent the gas extraction system fromreleasing landfill gas into the atmosphere, or make adjustments toreduce or stop release of landfill gas into the atmosphere.

FIG. 20 illustrates an example environment 2000 in which aspects of thetechnology described herein may be implemented. The environment 2000includes a landfill 2002 with decomposing waste 2004. The decomposingwaste may generate landfill gas 2006 that flows out from the landfill2002 through piping of a collection well 2008. The well 2008 is coupledto a control system 2010 that controls a flow of landfill gas throughpiping of the collection well 2008. A gas collection system 2012collects the landfill gas extracted from the well 2008. The collectedlandfill gas may be stored, used, or provided to another entity for use.For example, the collected landfill gas may be used by a power plant togenerate electricity. As another example, the collected landfill gas maybe treated in a gas processing plant to obtain methane from the landfillgas. For example, the landfill gas may be treated to remove oxygen,carbon dioxide, and/or another gas from the landfill gas. The methanegas may then be transported by a gas distribution system.

In some embodiments, the gas collection system 2012 includes a vacuumsource. The vacuum source generates a negative pressure differentialbetween the gas collection system 2012 and the landfill 2002. Thenegative pressure differential causes landfill gas to flow from thelandfill 2002 to the gas collection system through the well 2008. Insome embodiments, the gas collection system 2012 may be gas collectionsystem 1512 described above with reference to FIG. 15.

In some embodiments, the control system 2010 may be configured tocontrol extraction of landfill gas at the well 2010. Example controlsystems are described above with reference to FIGS. 1-3. In the exampleembodiment of FIG. 20, the control system 2010 includes a controller2010A configured to control a valve 2010B to control flow of landfillgas through the well piping. In some embodiments, the controller 2010Amay be configured to control a position of the valve 2010B to control aflow rate of landfill gas flowing through the well piping. Examples ofvalves are discussed herein. In some embodiments, the valve 2010B may bea throttle as described in U.S. patent application Ser. No. 16/510,167,titled “LANDFILL GAS EXTRACTION SYSTEM THROTTLE,” filed on Jul. 12,2019, which is incorporated by reference in its entirety herein. Thecontrol system 2010 includes an upstream pressure sensor 2010C formeasuring landfill gas pressure at a location upstream of the valve2010B, and a downstream pressure sensor 2010D for measuring landfill gaspressure at a location downstream of the valve 2010B. Example pressuresensors are discussed herein.

Landfill gas pressure at a location upstream of a valve may also bereferred to herein as “landfill gas pressure upstream of the valve,”and/or “upstream landfill gas pressure.” Landfill gas pressure at alocation downstream of a valve may also be referred to herein as“landfill gas pressure downstream of the valve,” and/or “downstreamlandfill gas pressure.”

In some embodiments, the controller 2010A may be configured to use ameasurement of landfill gas pressure at the location upstream of thevalve 2010B obtained from the pressure sensor 2010C to determine whetherthe gas extraction system is in a condition in which there is a risk oflandfill gas being released into the atmosphere. In some embodiments,the controller 2010A may be configured to determine whether themeasurement of landfill gas pressure at the location upstream of thevalve 2010B is greater than a threshold pressure. The controller 2010Amay be configured to take corrective action in response to determiningthat the measurement of landfill gas pressure at the location upstreamof the valve is greater than the threshold pressure. For example, thecontroller 2010A may be configured to control the valve 2010B to reducethe landfill gas pressure upstream of the valve and, as a result,prevent, reduce, or stop release of landfill gas into the atmosphere. Insome embodiments, the controller 2010A may be configured to change adegree to which the valve 2010B is open to change the landfill gaspressure upstream of the valve. For example, the controller 2010A mayrotate the valve 2010B to open the valve 2010B further to cause areduction in landfill pressure upstream of the valve.

In some embodiments, the controller 2010A may be configured to determineif the landfill gas pressure at a location downstream of the valve isless than a threshold pressure based on a measurement obtained from thedownstream pressure sensor 2010D to determine if there is sufficientnegative landfill gas pressure downstream of the valve to use to reducethe landfill gas pressure upstream of the valve. For example, thecontroller 2010A may determine whether the measurement of the landfillgas pressure at the location downstream of the valve 2010B is negative.In some embodiments, the controller 2010A may be configured to determineto change a position of the valve 2010B based on the measurement of thelandfill gas pressure at the location downstream of the valve to ensurethat the valve 2010B is only opened further if there is sufficientnegative landfill gas pressure downstream of the valve 2010B that may beused to reduce the pressure upstream of the valve 2010B. For example,the controller 2010A may determine to increase the degree to which thevalve 2010B is open if the controller 2010A determines that (1) thelandfill gas pressure at the location upstream of the valve is positive,and (2) the landfill gas pressure at the location downstream of thevalve measured by the pressure sensor 2010D is negative. As anotherexample, the controller 2010A may determine to increase the degree towhich the valve 2010B is open if the controller 2010A determines that(1) the landfill gas pressure at the location upstream of the valve isabove a threshold (e.g., −0.1 MBar), and (2) the landfill gas pressureat the location downstream of the valve measured by the pressure sensor2010D is negative.

In some embodiments, the controller 2010A may be a local controller tothe well 2008. For example, controller 2010A may be one of controller1510A-C described above with reference to FIG. 15. In some embodiments,the controller 2010A may be remote from the well 2008. The controller2010A may be in communication with an actuator and/or sensors 2010C-Dlocated at the well 2008 to remotely control the valve 2010B.

In some embodiments, the controller 2010A may be configured to controlthe valve 2010B to reduce the landfill gas pressure upstream of thevalve 2010B by not implementing one or more other adjustments inposition determined for the valve based on other control inputs (e.g.,vacuum pressure change, barometric pressure change, ambient temperaturechange, field level adjustment inputs). For example, if the controller2010A detects that the landfill gas pressure upstream of the valve 2010Bis greater than a threshold pressure, the controller 2010A may bypassthe other adjustments in position determined for the valve 2010B.

In some embodiments, the controller 2010A may be configured to use themeasurement of landfill gas pressure at the location upstream of thevalve 2010B and/or a determination of whether the measured landfill gaspressure at the location upstream of the valve 2010B exceeds a thresholdpressure as an input to use in combination with other inputs todetermine an adjustment in position for the valve 2010B. For example,the controller 2010A may be configured to use the measured landfill gaspressure at the location upstream of the valve 2010B as an additionalinput to inputs 1702A-E described above with reference to FIG. 17 todetermine a cumulative adjustment to the valve position 2010B based onmultiple different inputs.

In some embodiments, the controller 2010A may be configured to store arecord of a detected state in which there was a risk of releasinglandfill gas into the atmosphere. Regulators (e.g., government) mayrequire reporting of cases in which there is a risk of landfill gasreleasing landfill gas into the atmosphere, and a record of correctiveaction. To comply with these requirements, the controller 2010A may beconfigured to automatically store a record of when the measured landfillgas pressure at the location upstream of the valve 2010B exceeds athreshold pressure. For example, the controller 2010A may store atimestamp, and measurement of the landfill gas pressure at the locationupstream of the valve 2010B in response to detecting a state in whichthere is a risk of landfill gas being released into the atmosphere. Insome embodiments, the controller 2010A may be configured to store arecord of corrective action taken by the controller 2010A. For example,the controller 2010A may store one or more adjustments made to theposition of the valve 2010B, and/or one or more measurements of thelandfill gas pressure upstream of the valve 2010B subsequent to theadjustment(s). In some embodiments, the controller 2010A may beconfigured to store a record of the measurement(s) of the landfill gaspressure upstream of the valve subsequent to the adjustment(s) when thecontroller 2010A has detected that the measurement(s) of the landfillgas pressure upstream of the valve is less than the threshold pressure(e.g., −0.1 mbar).

FIG. 21 is a flowchart of an illustrative process 2100 for controllingflow of landfill gas. Process 2100 may be performed at least in part bycontrol system 2010 described above with reference to FIG. 20.

Process 2100 begins at act 2102 where the system obtains a measurementof a landfill gas pressure at a location upstream of a valve of thesystem. For example, the system may obtain a measurement of landfill gaspressure upstream of the valve 2010B from pressure sensor 2010C. Thelandfill gas pressure upstream of the valve may be used by the system asan indication as to whether the gas extraction system is in a state, orapproaching a state, in which it may be releasing landfill gas into theatmosphere.

Next, process 2100 proceeds to act 2104, where the system determineswhether the measurement of landfill gas pressure upstream of the valveis greater than a first threshold pressure. In some embodiments, thefirst threshold pressure may be a pressure at which there is a risk oflandfill gas being released into the atmosphere. In some embodiments,the first threshold pressure is approximately −0.6 mbar, −0.5 mbar, −0.4mbar, −0.3 mbar, −0.2 mbar, −0.1 mbar, 0 mbar, 0.1 mbar, 0.2 mbar, 0.3mbar, 0.4 mbar, 0.5 mbar, or 0.6 mbar. In some embodiments, the firstthreshold pressure may be a variable value that is determined by thesystem. For example, the system may be configured to determine the firstthreshold pressure based on one or more environmental conditions (e.g.,barometric pressure, ambient temperature, and/or vacuum pressure).

If at act 2104 the system determines that the measurement of landfillgas pressure upstream of the valve is less than the first thresholdpressure, then process 2100 returns to act 2102 where the system againobtains a measurement of the landfill gas pressure upstream of thevalve. The system may determine that there is no corrective action to betaken based on the measurement of the landfill gas pressure upstream ofthe valve. For example, the system may maintain a current position ofthe valve. As another example, the system may implement one or morevalve position adjustments determined based on control inputs (e.g.,ambient temperature change, barometric pressure change) other than themeasurement of landfill gas pressure upstream of the valve.

In some embodiments, the system may be configured to obtain ameasurement of the landfill gas pressure upstream of the valve at aregular interval. For example, the system may obtain a measurement everysecond, minute, or hour. Some embodiments are not limited to aparticular frequency of obtaining measurements of the landfill gaspressure upstream of the valve.

If at act 2104 the system determines that the measurement of landfillgas pressure upstream of the valve is greater than the first thresholdpressure, then process 2100 process to act 2106 where the system obtainsa measurement of landfill gas pressure at a location downstream of thevalve. For example, the system may obtain a measurement of the landfillgas pressure downstream of the valve 2010B from pressure sensor 2010Ddescribed above with reference to FIG. 20. The measurement of landfillgas pressure downstream of the valve may be used as an indication as towhether there is negative landfill gas pressure downstream of the valvethat can be utilized to reduce the landfill gas pressure upstream of thevalve.

After obtaining the measurement of landfill gas pressure downstream ofthe valve at act 2106, process 2100 proceeds to act 2108 where thesystem determines whether the landfill gas pressure downstream of thevalve is less than a second threshold pressure. In some embodiments, thesecond threshold pressure may be a pressure at which opening the valvemay reduce the pressure upstream of the valve. For example, if there isnegative landfill gas pressure downstream of the valve, opening thevalve may reduce the landfill gas pressure upstream of the valve. Insome embodiments, the second threshold pressure is approximately −5mbar, −4 mbar, −3 mbar, −2 mbar, −1 mbar, 0 mbar. In some embodiments,the second threshold pressure may be a variable value that is determinedby the system. For example, the system may determine the secondthreshold pressure based on the landfill gas pressure upstream of thevalve. The system may set the threshold pressure to a value less thanthe measured landfill gas pressure upstream of the valve to ensure thatopening the valve results in reduction of landfill gas pressure upstreamof the valve.

If at act 2108 the system determines that the measurement of landfillgas pressure downstream of the valve is less than the second thresholdpressure, then process 2100 proceeds to act 2102. In some embodiments,the system may be configured to maintain the valve at a currentposition, as there is not sufficient pressure differential between thelandfill gas pressure upstream of the valve and the landfill gaspressure downstream of the valve to reduce the landfill gas pressureupstream of the valve by opening the valve. For example, if the landfillgas pressure downstream of the valve is not negative, opening the valvefurther may result in increasing the landfill gas pressure upstream ofthe valve. This in turn may increase the release of landfill gas intothe atmosphere.

If at act 2108 the system determines that the landfill gas pressuredownstream of the valve is less than the second threshold pressure, thenprocess 2100 proceeds to act 2110, where the system opens the valve by afirst amount. In some embodiments, the system may be configured tospecify a percentage to set the position of the valve. For example, 0%may be a fully closed valve, and 100% may be a fully open valve. At act2110, the system may be configured to open the valve by a certainpercentage. For example, the system may open the valve by 1%, 2%, 3%,4%, 5%, 10%, 15%, 20%, or 25%, In some embodiments, the system may beconfigured to specify a rotational position of the valve. For example, 0degrees may be fully closed, and 180 degrees may be fully opened. At act2110, the system may be configured to open the valve by a certain numberof degrees. For example, the system may open the valve by 1, 2, 3, 4, 5,10, 15, 20, or 25 degrees. In some embodiments, the system may beconfigured to open the valve by an amount that is proportional to aratio of the landfill gas pressure upstream of the valve to a thresholdpressure value. In some embodiments, the threshold pressure value may be−5 mbar, −4 mbar, −3 mbar, −2 mbar, −1 mbar, 1 mbar, 2 mbar, 3 mbar, 4mbar, or 5 mbar.

After opening the valve by the first amount at act 2110, process 2100proceeds to act 2102 where the system again obtains a measurement of thelandfill gas pressure upstream of the valve (e.g., from pressure sensor2010C). In some embodiments, the system may be configured to makeincremental changes (e.g., by the first amount) in position of the valveuntil the landfill gas pressure upstream of the valve is less than thefirst threshold. Obtaining a new measurement of the landfill gaspressure upstream of the valve after opening the valve by the firstamount may provide the system with an indication of an effect that theadjustment had on the landfill gas pressure upstream of the valve.

In some embodiments, the system may be configured to prevent furtheradjustments if a measurement of landfill gas pressure upstream of thevalve obtained after making an adjustment in valve position results inan undesired effect. For example, if the landfill gas pressure upstreamof the valve increases in response to the adjustment, the system mayprevent subsequent adjustments in the same direction (e.g., opening thevalve further).

In some embodiments, the system may be configured to repeat process 2100at a regular interval (e.g., every second, minute, hour, and/or day). Insome embodiments, this may allow the system to detect a risk ofreleasing landfill gas into the atmosphere during all times of operationof the gas extraction system, and take corrective action in response.This ensures that the gas extraction system mitigates release oflandfill gas into the atmosphere, and also automatically meetsoperational requirements by automatically taking corrective action anddocumenting effects of the corrective action.

FIG. 11 illustrates an example of a suitable computing systemenvironment 1100 on which techniques disclosed herein may beimplemented. In some embodiments, portions of a landfill gas extractioncontrol system may be implemented in a computing system environment. Forexample, in some embodiments, Device Manager 502, Controller Module 504,User Interface 508, and/or Database 510 may be implemented in acomputing system environment. In some embodiments, aspects of one ormore techniques described herein may be implemented in a computingsystem environment.

The computing system environment 1100 is only one example of a suitablecomputing environment and is not intended to suggest any limitation asto the scope of use or functionality of the devices and techniquesdisclosed herein. Neither should the computing environment 1100 beinterpreted as having any dependency or requirement relating to any oneor combination of components illustrated in the exemplary operatingenvironment 1100.

The techniques disclosed herein are operational with numerous othergeneral purpose or special purpose computing system environments orconfigurations. Examples of well-known computing systems, environments,and/or configurations that may be suitable for use with techniquesdisclosed herein include, but are not limited to, personal computers,server computers, hand-held devices (e.g., smart phones, tabletcomputers, or mobile phones), laptop devices, multiprocessor systems,microprocessor-based systems, set top boxes, programmable consumerelectronics, network PCs, minicomputers, mainframe computers,distributed computing environments that include any of the above systemsor devices, and the like.

The computing environment may execute computer-executable instructions,such as program modules. Generally, program modules include routines,programs, objects, components, data structures, etc. that performparticular tasks or implement particular abstract data types. Theinvention may also be practiced in distributed computing environmentswhere tasks are performed by remote processing devices that are linkedthrough a communications network. In a distributed computingenvironment, program modules may be located in both local and remotecomputer storage media including memory storage devices.

With reference to FIG. 11, an exemplary system for implementingtechniques described herein includes a general purpose computing devicein the form of a computer 1110. Components of computer 1110 may include,but are not limited to, a processing unit 1120, a system memory 1130,and a system bus 1121 that couples various system components includingthe system memory to the processing unit 1120. The system bus 1121 maybe any of several types of bus structures including a memory bus ormemory controller, a peripheral bus, and/or a local bus using any of avariety of bus architectures. By way of example, and not limitation,such architectures include Industry Standard Architecture (ISA) bus,Micro Channel Architecture (MCA) bus, Enhanced ISA (EISA) bus, VideoElectronics Standards Association (VESA) local bus, and PeripheralComponent Interconnect (PCI) bus also known as Mezzanine bus.

Computer 1110 typically includes a variety of computer readable media.Computer readable media can be any available media that can be accessedby computer 1110 and includes both volatile and nonvolatile media,removable and non-removable media. By way of example, and notlimitation, computer readable media may comprise computer storage mediaand communication media. Computer storage media includes both volatileand nonvolatile, removable and non-removable media implemented in anymethod or technology for storage of information such as computerreadable instructions, data structures, program modules or other data.Computer storage media includes, but is not limited to, RAM, ROM,EEPROM, flash memory or other memory technology, CD-ROM, digitalversatile disks (DVD) or other optical disk storage, magnetic cassettes,magnetic tape, magnetic disk storage or other magnetic storage devices,or any other medium which can be used to store the desired informationand which can accessed by computer 1110. Communication media typicallyembodies computer readable instructions, data structures, programmodules or other data in a modulated data signal such as a carrier waveor other transport mechanism and includes any information deliverymedia. The term “modulated data signal” means a signal that has one ormore of its characteristics set or changed in such a manner as to encodeinformation in the signal. By way of example, and not limitation,communication media includes wired media such as a wired network ordirect-wired connection, and wireless media such as acoustic, RF,infrared and other wireless media. Combinations of the any of the aboveshould also be included within the scope of computer readable media.

The system memory 1130 includes computer storage media in the form ofvolatile and/or nonvolatile memory such as read only memory (ROM) 1131and random access memory (RAM) 1132. A basic input/output system 1133(BIOS), containing the basic routines that help to transfer informationbetween elements within computer 1110, such as during start-up, istypically stored in ROM 1131. RAM 1132 typically contains data and/orprogram modules that are immediately accessible to and/or presentlybeing operated on by processing unit 1120. By way of example, and notlimitation, FIG. 11 illustrates operating system 1134, applicationprograms 1135, other program modules 1136, and program data 1137.

The computer 1110 may also include other removable/non-removable,volatile/nonvolatile computer storage media. By way of example only,FIG. 11 illustrates a hard disk drive 1141 that reads from or writes tonon-removable, nonvolatile magnetic media, a magnetic disk drive 1151that reads from or writes to a removable, nonvolatile magnetic disk1152, and an optical disk drive 1155 that reads from or writes to aremovable, nonvolatile optical disk 1156 such as a CD ROM or otheroptical media. Other removable/non-removable, volatile/nonvolatilecomputer storage media that can be used in the exemplary operatingenvironment include, but are not limited to, magnetic tape cassettes,flash memory cards, digital versatile disks, digital video tape, solidstate RAM, solid state ROM, and the like. The hard disk drive 1141 istypically connected to the system bus 1121 through an non-removablememory interface such as interface 1140, and magnetic disk drive 1151and optical disk drive 1155 are typically connected to the system bus1121 by a removable memory interface, such as interface 1150.

The drives and their associated computer storage media discussed aboveand illustrated in FIG. 11, provide storage of computer readableinstructions, data structures, program modules and other data for thecomputer 1110. In FIG. 11, for example, hard disk drive 1141 isillustrated as storing operating system 1144, application programs 1145,other program modules 1146, and program data 1147. Note that thesecomponents can either be the same as or different from operating system1134, application programs 1135, other program modules 1136, and programdata 1137. Operating system 1144, application programs 1145, otherprogram modules 1146, and program data 1147 are given different numbershere to illustrate that, at a minimum, they are different copies. A usermay enter commands and information into the computer 1110 through inputdevices such as a keyboard 1162 and pointing device 1161, commonlyreferred to as a mouse, trackball or touch pad. Other input devices (notshown) may include a microphone, joystick, game pad, satellite dish,scanner, or the like. These and other input devices are often connectedto the processing unit 1120 through a user input interface 1160 that iscoupled to the system bus, but may be connected by other interface andbus structures, such as a parallel port, game port or a universal serialbus (USB). A monitor 1191 or other type of display device is alsoconnected to the system bus 1121 via an interface, such as a videointerface 1190. In addition to the monitor, computers may also includeother peripheral output devices such as speakers 1197 and printer 1196,which may be connected through a output peripheral interface 1195.

The computer 1110 may operate in a networked environment using logicalconnections to one or more remote computers, such as a remote computer1180. The remote computer 1180 may be a personal computer, a server, arouter, a network PC, a peer device or other common network node, andtypically includes many or all of the elements described above relativeto the computer 1110, although only a memory storage device 1181 hasbeen illustrated in FIG. 11. The logical connections depicted in FIG. 11include a local area network (LAN) 1171 and a wide area network (WAN)1173, but may also include other networks. Such networking environmentsare commonplace in offices, enterprise-wide computer networks, intranetsand the Internet.

When used in a LAN networking environment, the computer 1110 isconnected to the LAN 1171 through a network interface or adapter 1170.When used in a WAN networking environment, the computer 1110 typicallyincludes a modem 1172 or other means for establishing communicationsover the WAN 1173, such as the Internet. The modem 1172, which may beinternal or external, may be connected to the system bus 1121 via theuser input interface 1160, or other appropriate mechanism. In anetworked environment, program modules depicted relative to the computer1110, or portions thereof, may be stored in the remote memory storagedevice. By way of example, and not limitation, FIG. 11 illustratesremote application programs 1185 as residing on memory device 1181. Itwill be appreciated that the network connections shown are exemplary andother means of establishing a communications link between the computersmay be used.

Embodiments of the above-described techniques can be implemented in anyof numerous ways. For example, the embodiments may be implemented usinghardware, software or a combination thereof. When implemented insoftware, the software code can be executed on any suitable processor orcollection of processors, whether provided in a single computer ordistributed among multiple computers. In some embodiments, the functionsperformed by an In Situ Control Mechanism 106 and/or a Controller 204may be implemented as software executed on one or more processors.

Such processors may be implemented as integrated circuits, with one ormore processors in an integrated circuit component, includingcommercially available integrated circuit components known in the art bynames such as CPU chips, GPU chips, microprocessor, microcontroller, orco-processor. Alternatively, a processor may be implemented in customcircuitry, such as an ASIC, or semicustom circuitry resulting fromconfiguring a programmable logic device. As yet a further alternative, aprocessor may be a portion of a larger circuit or semiconductor device,whether commercially available, semicustom or custom. As a specificexample, some commercially available microprocessors have multiple coressuch that one or a subset of those cores may constitute a processor.Though, a processor may be implemented using circuitry in any suitableformat.

Further, it should be appreciated that a computer may be embodied in anyof a number of forms, such as a rack-mounted computer, a desktopcomputer, a laptop computer, or a tablet computer. Additionally, acomputer may be embedded in a device not generally regarded as acomputer but with suitable processing capabilities, including a PersonalDigital Assistant (PDA), a smart phone or any other suitable portable orfixed electronic device.

Also, a computer may have one or more input and output devices. Thesedevices can be used, among other things, to present a user interface.Examples of output devices that can be used to provide a user interfaceinclude printers or display screens for visual presentation of outputand speakers or other sound generating devices for audible presentationof output. Examples of input devices that can be used for a userinterface include keyboards, and pointing devices, such as mice, touchpads, and digitizing tablets. As another example, a computer may receiveinput information through speech recognition or in other audible format.

Such computers may be interconnected by one or more networks in anysuitable form, including as a local area network or a wide area network,such as an enterprise network or the Internet. Such networks may bebased on any suitable technology and may operate according to anysuitable protocol and may include wireless networks, wired networks orfiber optic networks.

Also, the various methods or processes outlined herein may be coded assoftware that is executable on one or more processors that employ anyone of a variety of operating systems or platforms. Additionally, suchsoftware may be written using any of a number of suitable programminglanguages and/or programming or scripting tools, and also may becompiled as executable machine language code or intermediate code thatis executed on a framework or virtual machine.

In this respect, the invention may be embodied as a computer readablestorage medium (or multiple computer readable media) (e.g., a computermemory, one or more floppy discs, compact discs (CD), optical discs,digital video disks (DVD), magnetic tapes, flash memories, circuitconfigurations in Field Programmable Gate Arrays or other semiconductordevices, or other tangible computer storage medium) encoded with one ormore programs that, when executed on one or more computers or otherprocessors, perform methods that implement the various embodiments ofthe invention discussed above. As is apparent from the foregoingexamples, a computer readable storage medium may retain information fora sufficient time to provide computer-executable instructions in anon-transitory form. Such a computer readable storage medium or mediacan be transportable, such that the program or programs stored thereoncan be loaded onto one or more different computers or other processorsto implement various aspects of the present invention as discussedabove. As used herein, the term “computer-readable storage medium”encompasses only a computer-readable medium that can be considered to bea manufacture (i.e., article of manufacture) or a machine. Alternativelyor additionally, the invention may be embodied as a computer readablemedium other than a computer-readable storage medium, such as apropagating signal.

The terms “program” or “software” are used herein in a generic sense torefer to any type of computer code or set of computer-executableinstructions that can be employed to program a computer or otherprocessor to implement various aspects of the present invention asdiscussed above. Additionally, it should be appreciated that accordingto one aspect of this embodiment, one or more computer programs thatwhen executed perform methods of the present invention need not resideon a single computer or processor, but may be distributed in a modularfashion amongst a number of different computers or processors toimplement various aspects of the present invention.

Computer-executable instructions may be in many forms, such as programmodules, executed by one or more computers or other devices. Generally,program modules include routines, programs, objects, components, datastructures, etc. that perform particular tasks or implement particularabstract data types. Typically the functionality of the program modulesmay be combined or distributed as desired in various embodiments.

Also, data structures may be stored in computer-readable media in anysuitable form. For simplicity of illustration, data structures may beshown to have fields that are related through location in the datastructure. Such relationships may likewise be achieved by assigningstorage for the fields with locations in a computer-readable medium thatconveys relationship between the fields. However, any suitable mechanismmay be used to establish a relationship between information in fields ofa data structure, including through the use of pointers, tags or othermechanisms that establish relationship between data elements.

Various aspects of the present invention may be used alone, incombination, or in a variety of arrangements not specifically discussedin the embodiments described in the foregoing and is therefore notlimited in its application to the details and arrangement of componentsset forth in the foregoing description or illustrated in the drawings.For example, aspects described in one embodiment may be combined in anymanner with aspects described in other embodiments.

Also, the invention may be embodied as a method, of which an example hasbeen provided. The acts performed as part of the method may be orderedin any suitable way. Accordingly, embodiments may be constructed inwhich acts are performed in an order different than illustrated, whichmay include performing some acts simultaneously, even though shown assequential acts in illustrative embodiments.

Various events/acts are described herein as occurring or being performedat a specified time. One of ordinary skill in the art would understandthat such events/acts may occur or be performed at approximately thespecified time.

Use of ordinal terms such as “first,” “second,” “third,” etc., in theclaims to modify a claim element does not by itself connote anypriority, precedence, or order of one claim element over another or thetemporal order in which acts of a method are performed, but are usedmerely as labels to distinguish one claim element having a certain namefrom another element having a same name (but for use of the ordinalterm) to distinguish the claim elements.

The terms “approximately,” “substantially,” and “about” may be used tomean within ±20% of a target value in some embodiments, within ±10% of atarget value in some embodiments, within ±5% of a target value in someembodiments, and yet within ±2% of a target value in some embodiments.The terms “approximately” and “about” may include the target value.

Also, the phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting. The use of“including,” “comprising,” or “having,” “containing,” “involving,” andvariations thereof herein, is meant to encompass the items listedthereafter and equivalents thereof as well as additional items.

Having thus described several aspects of at least one embodiment of thisinvention, it is to be appreciated that various alterations,modifications, and improvements will readily occur to those skilled inthe art.

Such alterations, modifications, and improvements are intended to bepart of this disclosure, and are intended to be within the spirit andscope of the invention. Further, though advantages of the presentinvention are indicated, it should be appreciated that not everyembodiment of the invention will include every described advantage. Someembodiments may not implement any features described as advantageousherein and in some instances. Accordingly, the foregoing description anddrawings are by way of example only.

What is claimed is:
 1. A control system for controlling extraction oflandfill gas from a landfill via a gas extraction system, the gasextraction system comprising well piping for coupling a well to a gasoutput, the control system comprising: a valve for controlling flow oflandfill gas through the well piping to the gas output; a pressuresensor configured to measure landfill gas pressure in the well piping ata location upstream of the valve; and a controller configured to:obtain, using the pressure sensor, a first measurement of the landfillgas pressure at the location upstream of the valve; determine whetherthe first measurement of the landfill gas pressure at the locationupstream of the valve is greater than a first threshold pressure; and inresponse to determining that the first measurement of the landfill gaspressure at the location upstream of the valve is greater than the firstthreshold pressure, control the valve to reduce the landfill gaspressure at the location upstream of the valve.
 2. The control system ofclaim 1, wherein the controller is configured to control the valve toreduce the landfill gas pressure in the well piping at the locationupstream of the valve by increasing a degree to which the valve is open.3. The control system of claim 2, wherein the controller is configuredto control the valve to reduce the landfill gas pressure in the wellpiping at the location upstream of the valve by: obtaining a secondmeasurement of landfill gas pressure in the well piping at a locationdownstream of the valve; determining whether the second measurement ofthe landfill gas pressure at the location downstream of the valve isless than a second threshold pressure; and increasing the degree towhich the valve is open only in response to determining that the secondmeasurement of the landfill gas pressure at the location downstream ofthe valve is less than the second threshold pressure.
 4. The controlsystem of claim 3, wherein the controller is configured to control thevalve to reduce the landfill gas pressure at the location upstream ofthe valve by maintaining a position of the valve in response todetermining that the second measurement of the landfill gas pressure atthe location downstream of the valve is greater than the secondthreshold pressure.
 5. The control system of claim 3, wherein the secondthreshold pressure is approximately 0 mbar.
 6. The control system ofclaim 1, wherein the first threshold pressure is approximately −0.1mbar.
 7. The control system of claim 1, wherein the controller isconfigured to control the valve to reduce the landfill gas pressure inthe well piping at the location upstream of the valve by: increasing adegree to which the valve is open by a first amount; and afterincreasing the degree to which the valve is open by the first amount:obtaining, from the pressure sensor, a second measurement of thelandfill gas pressure at the location upstream of the valve; and inresponse to determining that the second measurement of the landfill gaspressure at the location upstream of the valve is greater than the firstthreshold pressure, increasing the degree to which the valve is open bythe first amount.
 8. The control system of claim 1, wherein thecontroller is configured to: in response to determining that the firstmeasurement of the landfill gas pressure at the location upstream of thevalve is greater than the first threshold pressure: store a record ofthe first measurement of the landfill gas pressure at the locationupstream of the valve; store a record of controlling the valve to reducethe landfill gas pressure at the location upstream of the valve; andstore a record of a second measurement of the landfill gas pressure atthe location upstream of the valve after controlling the valve to reducethe landfill gas pressure at the location upstream of the valve.
 9. Thecontrol system of claim 8, wherein the controller is configured to:store the record of the second measurement of the landfill gas pressureat the location upstream of the valve when it is determined that thesecond measurement is less than the first threshold pressure.
 10. Thecontrol system of claim 1, wherein the controller is configured tocontrol the valve to reduce the landfill gas pressure at the locationupstream of the valve by: implementing one or more adjustments inposition of the valve determined by the controller for reducing thelandfill gas pressure at the location upstream of the valve; and notimplementing one or more other adjustments in the position of the valvedetermined by the controller.
 11. The control system of claim 1, whereinthe controller is configured to: in response to determining that thefirst measurement of the landfill gas pressure at the location upstreamof the valve is less than or equal to the first threshold pressure,control the valve by maintaining a position of the valve.
 12. A methodof controlling extraction of landfill gas from a landfill via a gasextraction system, the method comprising: obtaining, from a pressuresensor, a first measurement of landfill gas pressure at a locationupstream of a valve in well piping of the gas extraction system, thevalve being for controlling flow of landfill gas through the well pipingfrom the landfill to a gas output; determining whether the firstmeasurement of the landfill gas pressure at the location upstream of thevalve is greater than a first threshold pressure; and in response todetermining that the first measurement of the landfill gas pressure atthe location upstream of the valve is greater than the first thresholdpressure, controlling the valve to reduce the landfill gas pressure atthe location upstream of the valve.
 13. The method of claim 12, furthercomprising controlling the valve to reduce the landfill gas pressure inthe well piping at the location upstream of the valve by increasing adegree to which the valve is open.
 14. The method of claim 13, furthercomprising controlling the valve to reduce the landfill gas pressure inthe well piping at the location upstream of the valve by: obtaining asecond measurement of landfill gas pressure in the well piping at alocation downstream of the valve; determining whether the secondmeasurement of the landfill gas pressure at the location downstream ofthe valve is less than a second threshold pressure; and increasing thedegree to which the valve is open only in response to determining thatthe second measurement of the landfill gas pressure at the locationdownstream of the valve is less than the second threshold pressure. 15.The method of claim 14, further comprising controlling the valve toreduce the landfill gas pressure at the location upstream of the valveby maintaining a position of the valve in response to determining thatthe second measurement of the landfill gas pressure at the locationdownstream of the valve is greater than the second threshold pressure.16. The method of claim 14, wherein the second threshold pressure isapproximately 0 mbar.
 17. The method of claim 12, wherein the firstthreshold pressure is approximately −0.1 mbar.
 18. The method of claim12, further comprising controlling the valve to reduce the landfill gaspressure in the well piping at the location upstream of the valve by:increasing a degree to which the valve is open by a first amount; andafter increasing the degree to which the valve is open by the firstamount: obtaining, from the pressure sensor, a second measurement of thelandfill gas pressure at the location upstream of the valve; and inresponse to determining that the second measurement of the landfill gaspressure at the location upstream of the valve is greater than the firstthreshold pressure, increasing the degree to which the valve is open bythe first amount.
 19. The method of claim 12, further comprising: inresponse to determining that the first measurement of the landfill gaspressure at the location upstream of the valve is greater than the firstthreshold pressure: storing a record of the first measurement oflandfill gas pressure at the location upstream of the valve; storing arecord of controlling the valve to reduce the landfill gas pressure atthe location upstream of the valve; and storing a record of a secondmeasurement of the landfill gas pressure at the location upstream of thevalve after controlling the valve to reduce the landfill gas pressure atthe location upstream of the valve.
 20. The method of claim 19, furthercomprising: storing the record of the second measurement of the landfillgas pressure at the location upstream of the valve when it is determinedthat the second measurement is less than the first threshold pressure.21. The method of claim 12, further comprising controlling the valve toreduce the landfill gas pressure at the location upstream of the valveby: implementing one or more adjustments in position of the valvedetermined by the controller for reducing the landfill gas pressure atthe location upstream of the valve; and not implementing one or moreother adjustments in the position of the valve determined by thecontroller.
 22. The method of claim 12, further comprising: in responseto determining that the first measurement of the landfill gas pressureat the location upstream of the valve is less than or equal to the firstthreshold pressure, controlling the valve by maintaining a position ofthe valve.
 23. A control system for controlling extraction of landfillgas from a landfill via a gas extraction system, the gas extractionsystem comprising well piping for coupling a well to a gas output, thecontrol system comprising: a controller configured to: obtain a firstmeasurement of landfill gas pressure at a location upstream of a valvedisposed in the well piping, the valve being for controlling flow oflandfill gas through the well piping to the gas output; determinewhether the first measurement of the landfill gas pressure at thelocation upstream of the valve is greater than a first thresholdpressure; and in response to determining that the first measurement ofthe landfill gas pressure at the location upstream of the valve isgreater than the first threshold pressure, control the valve to reducethe landfill gas pressure at the location upstream of the valve.